Sure wish I had this when I was a mechanic's instructor. This is one of the most concise, well conceived and presented little video "vignettes" on this subject I have ever seen. WELL DONE SIR! Thank YOU!
I would like to add a note here, because it seems some people having trouble understanding it. Not all cdi's have this excitor coil, some old cdi's have that. Most of them nowdays have an inverter build in. These kinds of cdi's gets their power directly from the battery.
I have been teaching electronics at a local university, and will recommend my students to watch this video even though we don't go into power electronics. This is an excellent video describing the basics of a CDI system. There is supposed to be a signal conditioning circuit in the pulse rotator path that terminates at the SCR gate; its main function is to clean/filter the spikes from the triggering mechanism. All in all your explanation is very clear, and concise. Thanks for uploading the video.
Highly invaluable video, I saved a lot of time and money making my own CDI circuit from basically exactly this schematic for a 125cc dirt bike. 100ohm resistor, 1n4007 diodes, 1uf 250v cap and a BT169D thyristor.
Hi good work frank this project, I need to make this CDI of my dirt bike he is a suzuki rm 125 92 you know its work on my motorcycle? send me a e-mail please i realy need this project help me please, sende from: ph_monteiro2005@hotmail.com
HI All American Five today I opened an original dirt bike CDI, I can see to have a 250v orange capacitor, I am from Brazil, but I did not think to buy this cdi here and when I thought it was very expensive 450 500 $ How Do I understand enough of electronics to make my own cdi
Excellent description. Just what I was looking for. It's difficult for me to comprehend how my new CDI distributor on my 1974 Ford 302 V-8 manages to "trigger" with the components I see withing the distributor cap. Not that it makes an difference, but mine is a marine application. Thank you very much for the description.
I have been trying to learn and diagnose a small engine with no spark. these type videos are great ! Im almost amazed at the effort people put into these videos and the value that we all can get out of them. Im no engine or electronics expert but i know enough to fix some things and other times royally ruin things. I might be totally wrong but it doesn't make sense to me that the ignition's primary coil is grounded directly. I figured it would get the solid ground thru the gate(SCR/transistor or whatever it is)
Ha, brilliant! My mechanic just said my boat needed a trigger today, so when I found your video, it explained EXACTLY the info I wanted to understand. Kudos to you sir!!!!
Thanks Rick for uploading this video,, little bit of insight for others. Pulse coil is the one which would trigger when piston comes to top dead center in motor bikes. IN four stroke engine, u have intake(getting GA), compression(compress the GAS), spark(spark the compressed gas) and exhaust as four events, u want to spark the engine at the top of compression stroke, pulse coil will provide pulse exactly at that stage.. In Cars Transistor is used to pulse the coil ground and power is steady
I normally watch your radio videos. My 1984 Honda "Big Red" stopped running. What a pleasant surprise to find YOUR video covering this! Great job as always. The Big Red is running now, by the way. Thanks again my friend!
an excellent explanation. thank you. I had no idead what vehicle ignition was until yesterday, but watching this video, I can totally comprehend what vehicle ignition is and how CDI works.
I put a CDI system in a Ford 4 cylinder Cortina many years ago and straight away noticed more power and better idling , except one night i noticed that the engine was idling roughly when I opened the hood it looked like a Xmas tree, sparks leaking from all over the spark plug leads .The higher induced voltages must of been to much for the leads , the simple solution then was to buy HV insulating sleeve and install the leads inside.
Thanks Daniel, I've been busy working on a 50,000 Watt transmitter. Both three-phase circuit breakers failed. The station was off the air since Wednesday afternoon, got the parts in today and she's back on the air. Glad the video was helpful. Rick
Great explanation ! I envy your ability to simplify this to the point where anyone could understand... even after watching your video, I couldn't explain it so clearly. I get so caught up on details... I'd go off on a rant about timing advance curves, 2 cycle vs 4 cycle, coil fed vs battery fed ... and I'd walk frustrated and with the other person more confused than when I started.
Interesting. I was trying to figure out an Amazon review for a small engine accessory coil to provide 12 volts for gas engine bicycle lighting. This reviewer said that just adding the aftermarket coil (approx 180 degrees from the ignition charge coil) kept his engine from running more than 3,000 rpm. We used to do this exact trick with old Ducati and other euro "scrambler" dirt bikes that only had one magneto coil so we could get some lighting, and it was never a problem. Of course, those were the days of separate spark coils with contact breaker points (and incandescent lights that didn't care about the non-rectified AC pulse from the lighting coil), but still, I'm having a hard time understanding how adding another coil would possibly have any affect on the CDI system. The aftermarket coil is grounded to the engine and has one power lead coming from the other end of the coil, so both the ignition coil and the aftermarket lighting coil share the engine block as a ground - but that shouldn't be an issue... should it? Strange, eh?
Rich, Great information. This helps to understand various components. Now it also helps to see how the function in a radio or any other device. 73, Mike
CDI isn't the "black box" you thought it was. An SCR, v. a transistor, is used to ensure a more complete discharge of the capacitor to induce more voltage in the secondary coil. An SCR conducts until a reverse voltage is applied to its gate or, in this case, the capacitor fully discharges.
yes modern car have Cam sensor(provides which cylinder is top), and crank sensor(provides whether cylinder is approaching top dead or not) is fed to ECM/PCM, then PCM will send pulse signal to ICM(igniter) which will momentarily supply ground(using transistor switch on / off) to the ground side of the coil, note positive is 12 volt connected all the time, this makes a spark..
No pulse coil in car's. I would guess this is an ignition system for a lawnmower but this is just a guess. Modern automotive (and motorcycle) ignition systems are slightly more complex and use a crank sensor and a camshaft sensor (faster start times) and do not generate their own power from a magneto as this demo shows. All the other concepts are the same. Very nice demo Rick.
Yes without the diode operating the ignition stop switch would kill the engine and stop the ignition from firing. Without the diode there would be twice as much current through the exciter coil which also means twice as much heat. The designer of the circuit has determine that there would be no damage to the exciter coil by adding a diode, and ignition stop switch still stops the ignition from firing.
Excellent! I will use your video for reference when I get to this subject on motorcycle electrical systems. This is the quality of tutorial I remember from Airframe and Powerplant mechanics school years ago. (Mostly great quality WWII training films). JB
You prolly dont give a shit but does anybody know a method to get back into an instagram account..? I somehow lost the account password. I appreciate any tricks you can offer me.
@Kase Jayden thanks so much for your reply. I got to the site through google and I'm in the hacking process now. Seems to take quite some time so I will reply here later when my account password hopefully is recovered.
In addition to my other note, cars don't use CDI(capacitor discharge unit), rather it uses Transistor switching the ground side, with positive connected to positive side all the time.. hope my 2 notes would have made sense.. CDI is used in Motor bikes and transistor switching is used in Cars.
GREAT description of how a CDI works, easy to understand. I need to build a CDI for a motorcycle engine that uses two trigger coils. One at 10 BDTC and another at 35 BTDC. I assume I'd duplicate the SCR to the trigger circuit. But how would it "switch" to the 35 BTDC trigger as the engine speeds up? I need the advance to occur before 2,500 rpm.
This circuit is used in motor bikes. If you want to kill the engine, u use stop switch which will short the exciter coil to ground providing no current to spark plug and ur engine comes to stop.
the best explanation and workind of this circuit i have seen. my question on this is a ac cdi what is difference between dc/ac operation other tha alternating and direct?
Silicon Control Rectifier SCR Basic AC Circuit czcams.com/video/45H4J_S52Y4/video.html Silicon Control Rectifier SCR Basic DC Circuit czcams.com/video/ImyTwZGZ-Ls/video.html
The ground is the same ground everywhere just think of it as a wire. When the capacitor is charging the ground is negative, that negative goes up through the primary of the ignition coil making the right side of the capacitor negative. That makes the left side of the capacitor positive. Electrons will flow through a diode device against the arrow.
While looking at it with the electron flow view it makes perfect sense. Though it seems to confuse those eyeing the ground location of the capacitor/primary coil leg from a conventional current flow point of view.
Hello sir. Thank you for helping us along understand some of the mysteries of modern electrical automotive systems. I have a question if you don't mind. In a typical application of the CDI, how many "charge cycles' would you say is necessary to create enough charge in the capacitor? I ask because I really wonder how charging the capacitor is accomplished on say a single cylinder 2 stroke motorcycle engine. If a 2 stroke fires every single revolution of the crank shaft, and the CDI magnet system is tied to its rotation, then you pretty much only have 1 charge cycle (edit: 2 charge cycles) available for charging the capacitor. That is unless you use a gear system to speed up the shaft for the magnet system.
Well, the magneto rotor has multiple poles so there are many "charge cycles" per revolution. Also the pulse coil is usually on the flywheel so even 4 stroke bikes have 1 spark per revolution, a "wasted spark"
When the capacitor is charged, think of it like a battery. Positive on the left and negative on the right. When the SCR fires think of it like a wire. Now you have Positive and Negative voltage across the primary of the ignition coil.
Electrons flow from negative to positive. When the capacitor is charged and the SCR fires the electrons flow from the right side of the capacitor through the primary of the ignition coil up through the SCR to the positive side of the capacitor completing the closed circuit.
So electons flowing down from the right side of the capacitor don't see the ground as attractive and are eager (so to speak) to flow up to the left side of the capacitor.
Hello, what a great explanation of the cdi using that drawing. I do not have a wiring diagram of my CDI. What brought me here was an issue with my ATV whereby I have capacitor voltage (300v) at the primary of my coil all the time. I have a dc system and I'm unsure if the CDI is bad because the SCR is and being triggered all the time, or there is some other issue. Its a strange issue and I'm not alone as many have mentioned this issue but unfortunately I have yet to find an answer. Any light that you could shine would be extremely helpful for one wandering around in the dark.
If the SCR is good, it needs to be turned ON and then turned OFF. To troubleshot a circuit you need to know how each component functions. I did a viedo on a SCR, it may help you understand your circuit. Silicon Control Rectifier SCR Basic AC Circuit czcams.com/video/45H4J_S52Y4/video.html
@@AllAmericanFiveRadio Thank you so much for this. I will check it out. It would seem my SCR is always triggered on which surprises me because I thought it would fail open.
A very very good video! I actually learned a great deal. However I would like to respectfully challenge the circuit slightly, and I emphasize the word challenge because I am also unsure I am just throwing something out there. I believe one of the grounds should be in between the right side of the capacitor and above the primary side of the ignition coil. Instead of its current location in between the primary side of the ignition coil and after side SCR. But again, I am not sure, I just think it would be more right?! Please give me your thought. And thank you again, great simplified video, which gets right down to the point
When the SCR fires it is like a wire, and that supplies the ground. Silicon Control Rectifier SCR Basic AC Circuit czcams.com/video/45H4J_S52Y4/video.html
If I'm understanding this correctly, the maximum voltage that the capacitor can charge to is equal to the maximum voltage produced by the stator coil (excitor). Is this correct? From what other folks have said, on scooters at least, the stator coils produce around 60 - 100 volts.
If there's current flowing through the primary coil even with the trigger off, what's stopping the voltage from being stepped up to the secondary coil and firing?
Wouldn't the polarity be the opposite of what is shown? I would think the negative part of the cycle would be feeding electrons to the capacitor since electrons have a negative charge.
A rectifier (diode) only allows current to flow in one direction. To utilize the other half of the AC cycle, a diode bridge would be used (four diodes), and the circuit would also need to be reconfigured. Google “diode bridge”.
Transformer Basic Parts & Function czcams.com/video/q3YhbugYjJY/video.html Transformers, a few basics czcams.com/video/UvHCQswnjEg/video.html Transformers, basic phasing czcams.com/video/BRBqUQPLk-M/video.html
Hi Rick, Thank you for going to all the trouble to make this up and help a lot of people. One thought - you keep saying the capacitor is "storing voltage", or "a little more voltage is put into the capacitor" - I think what we mean is storing amperage, or storing current? I don't think capacitors store voltage, correct? Please correct me if I'm wrong. Thanks!
...so in a CDI ignition, the spark plug fires when the SCR switches the primary circuit "ON".? I have seen other systems where the firing circuit arrangement is such that the spark plug fires on the RELEASE of the primary voltage. Does this one fire the plug on the RISE of the PRIMARY coil (thus the RISE of the secondary)? THIS MAKES SENSE--I even tried it and it works fine!
....it's interesting. Top explanation was given in our homegrown Australia Electronics magazine 51 years ago and revisited in 1975. ..In conventional Kettering ignition system it is the sudden collapse of the built up magnetic field in the coil which built up in say period of ½ a millisecond collapsing in say ½ a microsecond that generates around 400 volts in primary of ignition coil ( (this phenomena for voltage boost isn't so familiar to many )) which then is instantly stepped up to around say 30 kilovolts by familiar transformer action of coil..With cdi however the 400 volts already is supplied available thus merely needs to be dumped by capacitor action across the primary instantaneously, and capacitors are very good for instantaneous dumping , a 1uf capacitor rated for at least 400 volts is plenty for high energy sparks up into very high revolutions for multi cylinder engines...Also cos it's the effect of forced voltage feed instead of magnetic collapse it turns out that the polarity of the spark is changed. The ideal is for the centre electrode to be negative cos it's hotter,, along lines of vacuum tubes,, but not a big deal . .gotta mention too maybe that in Kettering ignition that it's initially 12 volts across the primary that builds up to 400 upon magnetic collapse when ignition points break contact.
Capacitors, DC and AC Current czcams.com/video/NInt1Ss3vQ4/video.html AC Alternating Current, for the Beginner czcams.com/video/xVbqMFkyuXI/video.html Transformer Basic Parts & Function czcams.com/video/q3YhbugYjJY/video.html
Does this mean that the CDI boxes are standardized or is each one unique to the motor they fire? I'm having trouble finding a replacement for my CDI and was wondering if it could be remade easily.
Could you run it from 6 or 12v dc battery? Or is AC (no current cycle through diode) necessary to enable the SCR to shut off after it has been triggered?
Hi my friend, good video, I like to know if all kinds of pick up coils generate low voltage to excite the CDI? My engine is an RM 125 and 92, but it did not generate something voltage i think have a problem from my pick up coil, what do you think ?
Great informative video. I have a CDI on an older motorcycle. It only makes a spark once when I push the stop button and the rest of the time nothing. I'm thinking either the SCR is bad or the trigger coil is bad and the stop button is actually discharging the capacitor.
If the trigger is given to the SCR not only while starting the bike, does it mean that CDI is required even for running the bike smoothly? My motorcycle under cold conditions burps out for about 5-10 minutes past starting and switches off while the throttle is not revved (I set the idling to its best form but this still happens). Because of this fuel efficiency has severely been plummeted, do you think there might be a problem in the CDI. (I kind of related this to the CDI because my bike tremendously burps out through the silencer whenever i start).
Thanks for the demo was wondering how I could reverse engineer this and I think I can now. I have a bank of coils discharging into a network of caps. I then want to discharge these caps while effectively swapping the coils onto another bank of caps so I can charge these while discharging the other bank then swapping back to the other bank and then the whole sequence repeats. Just one query shouldnt the primary coils emf collapse as the cap discharges then induce into the secondary coil and across the spark gap?
Good video and explanation but the one thing that I feel is missing is an explanation of how the collapsing magnetic field in the primary winding relates to a spark being generated.
Transformer Basic Parts & Function czcams.com/video/q3YhbugYjJY/video.html Transformers, a few basics czcams.com/video/UvHCQswnjEg/video.html Impedance, Back EMF, AC Resistance czcams.com/video/y11SbmXPY18/video.html
Recall that primary and secondary are wound on the same core. A sudden drop in the primary's magnetic field produces the same drop in the secondary's field. Thus the secondary's terminals develop a voltage across them that is proportional to the rate of change of the magnetic field.
Sure wish I had this when I was a mechanic's instructor. This is one of the most concise, well conceived and presented little video "vignettes" on this subject I have ever seen. WELL DONE SIR! Thank YOU!
Thanks Jim Dixon
I would like to add a note here, because it seems some people having trouble understanding it. Not all cdi's have this excitor coil, some old cdi's have that. Most of them nowdays have an inverter build in. These kinds of cdi's gets their power directly from the battery.
I have been teaching electronics at a local university, and will recommend my students to watch this video even though we don't go into power electronics. This is an excellent video describing the basics of a CDI system. There is supposed to be a signal conditioning circuit in the pulse rotator path that terminates at the SCR gate; its main function is to clean/filter the spikes from the triggering mechanism. All in all your explanation is very clear, and concise. Thanks for uploading the video.
Thank you. I'm glad you find this video worthwhile watching and useful, and hope your students will also.
Such an awesome job! I am very visual learner and I’ll be watching this repeatedly. Thank you!!!
I'm glad this video is helping. THANKS!
This is the best explanation i have seen so far. Thanks
...and even his voice is so pleasant, a calm voice that is good to be heard!
Highly invaluable video, I saved a lot of time and money making my own CDI circuit from basically exactly this schematic for a 125cc dirt bike. 100ohm resistor, 1n4007 diodes, 1uf 250v cap and a BT169D thyristor.
Hi good work frank this project, I need to make this CDI of my dirt bike he is a suzuki rm 125 92 you know its work on my motorcycle? send me a e-mail please i realy need this project help me please, sende from: ph_monteiro2005@hotmail.com
Usually the capacitor is the part that fails first.
HI All American Five today I opened an original dirt bike CDI, I can see to have a 250v orange capacitor, I am from Brazil, but I did not think to buy this cdi here and when I thought it was very expensive 450 500 $ How Do I understand enough of electronics to make my own cdi
I'm glad the video helped
Do you believe this circuit meets my dirt bike? because shee reaches 11 000 rpm two stroke power monocylinder
Excellent description. Just what I was looking for. It's difficult for me to comprehend how my new CDI distributor on my 1974 Ford 302 V-8 manages to "trigger" with the components I see withing the distributor cap. Not that it makes an difference, but mine is a marine application. Thank you very much for the description.
I have been trying to learn and diagnose a small engine with no spark. these type videos are great !
Im almost amazed at the effort people put into these videos and the value that we all can get out of them.
Im no engine or electronics expert but i know enough to fix some things and other times royally ruin things.
I might be totally wrong but it doesn't make sense to me that the ignition's primary coil is grounded directly. I figured it would get the solid ground thru the gate(SCR/transistor or whatever it is)
Yes even 8 years later. fantastic!!
How to use eliminate,
And ,did you know how to create a klin spark ignition for ceramic factory
Glad you made this. Learning all the components and their contributions is hard enough but seeing any changes in a real time model, greatly helps
I'm glad you found this video useful.
Thank you, and your welcome.
Excellent video, thank you for taking the time to do this. I now completely understand how this system works. My 50 HP merc outboard uses this system.
Ha, brilliant! My mechanic just said my boat needed a trigger today, so when I found your video, it explained EXACTLY the info I wanted to understand. Kudos to you sir!!!!
Thanks
Thanks Rick for uploading this video,, little bit of insight for others. Pulse coil is the one which would trigger when piston comes to top dead center in motor bikes. IN four stroke engine, u have intake(getting GA), compression(compress the GAS), spark(spark the compressed gas) and exhaust as four events, u want to spark the engine at the top of compression stroke, pulse coil will provide pulse exactly at that stage.. In Cars Transistor is used to pulse the coil ground and power is steady
thank you very much for such a clear concise description of how the scr based cdi works.
I normally watch your radio videos. My 1984 Honda "Big Red" stopped running. What a pleasant surprise to find YOUR video covering this! Great job as always. The Big Red is running now, by the way. Thanks again my friend!
Thanks. I'm glad this video helped.
an excellent explanation. thank you. I had no idead what vehicle ignition was until yesterday, but watching this video, I can totally comprehend what vehicle ignition is and how CDI works.
THANKS
I put a CDI system in a Ford 4 cylinder Cortina many years ago and straight away noticed more power and better idling , except one night i noticed that the engine was idling roughly when I opened the hood it looked like a Xmas tree, sparks leaking from all over the spark plug leads .The higher induced voltages must of been to much for the leads , the simple solution then was to buy HV insulating sleeve and install the leads inside.
+190055joe THANKS
Thanks Daniel, I've been busy working on a 50,000 Watt transmitter. Both three-phase circuit breakers failed. The station was off the air since Wednesday afternoon, got the parts in today and she's back on the air.
Glad the video was helpful.
Rick
Great video on operation........Thanks for the explanation!
Great explanation ! I envy your ability to simplify this to the point where anyone could understand... even after watching your video, I couldn't explain it so clearly. I get so caught up on details... I'd go off on a rant about timing advance curves, 2 cycle vs 4 cycle, coil fed vs battery fed ... and I'd walk frustrated and with the other person more confused than when I started.
Thanks for your comment.
Thank You for this demonstration, everything was clear and understandable! Great job!
Thank you!
This is how my Honda Rebel 250 ignition system works.
Thank you for the visual explanation!
Thanks and your welcome.
Interesting. I was trying to figure out an Amazon review for a small engine accessory coil to provide 12 volts for gas engine bicycle lighting. This reviewer said that just adding the aftermarket coil (approx 180 degrees from the ignition charge coil) kept his engine from running more than 3,000 rpm. We used to do this exact trick with old Ducati and other euro "scrambler" dirt bikes that only had one magneto coil so we could get some lighting, and it was never a problem. Of course, those were the days of separate spark coils with contact breaker points (and incandescent lights that didn't care about the non-rectified AC pulse from the lighting coil), but still, I'm having a hard time understanding how adding another coil would possibly have any affect on the CDI system. The aftermarket coil is grounded to the engine and has one power lead coming from the other end of the coil, so both the ignition coil and the aftermarket lighting coil share the engine block as a ground - but that shouldn't be an issue... should it?
Strange, eh?
T would need to see the circuit.
Great explanation, thank you. Just for reference SCR stands for Silicon Controlled Rectifier.
Thanks
Wow, what a gift this video is to me. Great explanation, thank you!
Thanks and your welcome.
Rich, Great information. This helps to understand various components. Now it also helps to see how the function in a radio or any other device.
73,
Mike
CDI isn't the "black box" you thought it was. An SCR, v. a transistor, is used to ensure a more complete discharge of the capacitor to induce more voltage in the secondary coil. An SCR conducts until a reverse voltage is applied to its gate or, in this case, the capacitor fully discharges.
Silicon Control Rectifier SCR Basic AC Circuit
czcams.com/video/45H4J_S52Y4/video.html
yes modern car have Cam sensor(provides which cylinder is top), and crank sensor(provides whether cylinder is approaching top dead or not) is fed to ECM/PCM, then PCM will send pulse signal to ICM(igniter) which will momentarily supply ground(using transistor switch on / off) to the ground side of the coil, note positive is 12 volt connected all the time, this makes a spark..
You have a great way of explaning things, thank-you.
Thanks you, and your welcome.
FANTASTIC explanation.
Thanks
Excellent Demo, should be a teacher.
Thanks and your welcome.
Excellent video to understand how CDI functions along with magneto coil and spark plug.
Thanks
Dear Sir, you are too Experienced, appreciate your work.
THANK YOU!
Great video very clear and to the point with easy to understand illustration thank you sir👍
Thanks
Thats a analogic CDI, today we use DIGITAL CDI , always good video very clean diagram!
Send me a diagram of a digital CDI. Thanks.
Good video, excellent visualization. Thank you
Thanks
Very nicely explained, cct done in a very simple manner, easily understood.
This gentleman should do more projects ! Good teacher!
Thank you, and your welcome.
the silicone rectifier or SCR is a electric one way gate that's controlled by the pulsar coil.
Thank you for your explanation.
No pulse coil in car's. I would guess this is an ignition system for a lawnmower but this is just a guess. Modern automotive (and motorcycle) ignition systems are slightly more complex and use a crank sensor and a camshaft sensor (faster start times) and do not generate their own power from a magneto as this demo shows. All the other concepts are the same. Very nice demo Rick.
Kind Sir thank you so much, super clear and very well explained.
Thank you, hope this video helps.
Very nice of you. The best compliment. " I got it ".Thank you.
Yes without the diode operating the ignition stop switch would kill the engine and stop the ignition from firing. Without the diode there would be twice as much current through the exciter coil which also means twice as much heat. The designer of the circuit has determine that there would be no damage to the exciter coil by adding a diode, and ignition stop switch still stops the ignition from firing.
Thanks for clarifying how it works. This helps me a lot
Glad it helped. Thanks, and your welcome.
Great job! did you put all this animation together too?
Yes
Excellent! I will use your video for reference when I get to this subject on motorcycle electrical systems. This is the quality of tutorial I remember from Airframe and Powerplant mechanics school years ago. (Mostly great quality WWII training films). JB
You prolly dont give a shit but does anybody know a method to get back into an instagram account..?
I somehow lost the account password. I appreciate any tricks you can offer me.
@Duncan Jaxson Instablaster ;)
@Kase Jayden thanks so much for your reply. I got to the site through google and I'm in the hacking process now.
Seems to take quite some time so I will reply here later when my account password hopefully is recovered.
In addition to my other note, cars don't use CDI(capacitor discharge unit), rather it uses Transistor switching the ground side, with positive connected to positive side all the time.. hope my 2 notes would have made sense.. CDI is used in Motor bikes and transistor switching is used in Cars.
This explanation is really perfect
Thanks.
Your welcome.
The Best Video on CZcams !
THANK YOU!
Beautiful explanation! Thanks you so much.
Thank you, and your welcome.
GREAT description of how a CDI works, easy to understand. I need to build a CDI for a motorcycle engine that uses two trigger coils. One at 10 BDTC and another at 35 BTDC. I assume I'd duplicate the SCR to the trigger circuit. But how would it "switch" to the 35 BTDC trigger as the engine speeds up? I need the advance to occur before 2,500 rpm.
simple and straight to the point, thanks
Thank you, and your welcome.
Cool video Interesting to know how it really works animated . Since i work on this stuff everyday for the past 30 years as a Motorcycle / AtV Mechanic
Thanks
Finally a full understanding,,thank you sir.
Thanks and your welcome.
Very nice illustration. THANKS!
Thanks, and your welcome.
Thank you, with the video simulator above, I came to understand how the CDI works.
Thanks
Excellent explanation, thanks for your time and effort.
Thanks
Very very good video and good description, thank you so much
This circuit is used in motor bikes. If you want to kill the engine, u use stop switch which will short the exciter coil to ground providing no current to spark plug and ur engine comes to stop.
the best explanation and workind of this circuit i have seen. my question on this is a ac cdi what is difference between dc/ac operation other tha alternating and direct?
Silicon Control Rectifier SCR Basic AC Circuit
czcams.com/video/45H4J_S52Y4/video.html
Silicon Control Rectifier SCR Basic DC Circuit
czcams.com/video/ImyTwZGZ-Ls/video.html
Thank you for the informative program.
Thank you, and your welcome.
The ground is the same ground everywhere just think of it as a wire. When the capacitor is charging the ground is negative, that negative goes up through the primary of the ignition coil making the right side of the capacitor negative. That makes the left side of the capacitor positive. Electrons will flow through a diode device against the arrow.
While looking at it with the electron flow view it makes perfect sense.
Though it seems to confuse those eyeing the ground location of the capacitor/primary coil leg from a conventional current flow point of view.
Great job, thanks AllAmericanFiveRadio!
Thanks and your welcome.
Good explanation, i've ever seen...
Thank you
Thank you, and your welcome.
Very good teachings sir please upload more thank you
Thanks
THANKS FOR THE CLEAR EXPLANATION
Thanks
Гарна робота!!!
Thanks and your welcome.
Hello sir. Thank you for helping us along understand some of the mysteries of modern electrical automotive systems. I have a question if you don't mind. In a typical application of the CDI, how many "charge cycles' would you say is necessary to create enough charge in the capacitor? I ask because I really wonder how charging the capacitor is accomplished on say a single cylinder 2 stroke motorcycle engine. If a 2 stroke fires every single revolution of the crank shaft, and the CDI magnet system is tied to its rotation, then you pretty much only have 1 charge cycle (edit: 2 charge cycles) available for charging the capacitor. That is unless you use a gear system to speed up the shaft for the magnet system.
Don't know, the question was how does a CDI work. Give me a motor model and it's circuit. I'll try to explain the circuit.
Well, the magneto rotor has multiple poles so there are many "charge cycles" per revolution. Also the pulse coil is usually on the flywheel so even 4 stroke bikes have 1 spark per revolution, a "wasted spark"
When the capacitor discharges, why doesn't the electricty just flow to the frame via the ground that is between the SCR and the primary coil?
When the capacitor is charged, think of it like a battery. Positive on the left and negative on the right. When the SCR fires think of it like a wire. Now you have Positive and Negative voltage across the primary of the ignition coil.
Electrons flow from negative to positive. When the capacitor is charged and the SCR fires the electrons flow from the right side of the capacitor through the primary of the ignition coil up through the SCR to the positive side of the capacitor completing the closed circuit.
So electons flowing down from the right side of the capacitor don't see the ground as attractive and are eager (so to speak) to flow up to the left side of the capacitor.
@@robertbrandywine Yes. Except it's the magnetic field that shifts, not the electrons.
thanks the best explanation now I understand 👍
Thanks
Very clear explanation , Thanx for the video loved it
Crystal clear explanation. Thank you very much!
Thank you, and your welcome.
Hello, what a great explanation of the cdi using that drawing. I do not have a wiring diagram of my CDI. What brought me here was an issue with my ATV whereby I have capacitor voltage (300v) at the primary of my coil all the time. I have a dc system and I'm unsure if the CDI is bad because the SCR is and being triggered all the time, or there is some other issue. Its a strange issue and I'm not alone as many have mentioned this issue but unfortunately I have yet to find an answer. Any light that you could shine would be extremely helpful for one wandering around in the dark.
If the SCR is good, it needs to be turned ON and then turned OFF. To troubleshot a circuit you need to know how each component functions. I did a viedo on a SCR, it may help you understand your circuit.
Silicon Control Rectifier SCR Basic AC Circuit
czcams.com/video/45H4J_S52Y4/video.html
@@AllAmericanFiveRadio Thank you so much for this. I will check it out. It would seem my SCR is always triggered on which surprises me because I thought it would fail open.
A very very good video! I actually learned a great deal. However I would like to respectfully challenge the circuit slightly, and I emphasize the word challenge because I am also unsure I am just throwing something out there.
I believe one of the grounds should be in between the right side of the capacitor and above the primary side of the ignition coil. Instead of its current location in between the primary side of the ignition coil and after side SCR.
But again, I am not sure, I just think it would be more right?! Please give me your thought.
And thank you again, great simplified video, which gets right down to the point
Thank you, and your welcome.
An excellent video and description.
Thank you, and your welcome.
Excellent, especially with the "animation"!
Thanks
Very helpful for my training! Thanks!
Thanks and your welcome.
Just confused it looks lile the capacitor isnt grounding on the earth side? Wouldnt it ground and than have a negative charge on that plate?
When the SCR fires it is like a wire, and that supplies the ground.
Silicon Control Rectifier SCR Basic AC Circuit
czcams.com/video/45H4J_S52Y4/video.html
If I'm understanding this correctly, the maximum voltage that the capacitor can charge to is equal to the maximum voltage produced by the stator coil (excitor). Is this correct? From what other folks have said, on scooters at least, the stator coils produce around 60 - 100 volts.
Yes that's correct
Very clear explanation Rick.Thx a lot
If there's current flowing through the primary coil even with the trigger off, what's stopping the voltage from being stepped up to the secondary coil and firing?
When the capacitor is charging the current is not strong enough to produce a spark.
Wouldn't the polarity be the opposite of what is shown? I would think the negative part of the cycle would be feeding electrons to the capacitor since electrons have a negative charge.
A rectifier (diode) only allows current to flow in one direction. To utilize the other half of the AC cycle, a diode bridge would be used (four diodes), and the circuit would also need to be reconfigured. Google “diode bridge”.
Doesn't spark occur when the field collapses, not when the coil is being charged by the capacitor..e.g. after the trigger is past the trigger point ?
Transformer Basic Parts & Function
czcams.com/video/q3YhbugYjJY/video.html
Transformers, a few basics
czcams.com/video/UvHCQswnjEg/video.html
Transformers, basic phasing
czcams.com/video/BRBqUQPLk-M/video.html
appreciate it....great demonstration....keep up the good work :-)
Thanks
Hi Rick, Thank you for going to all the trouble to make this up and help a lot of people. One thought - you keep saying the capacitor is "storing voltage", or "a little more voltage is put into the capacitor" - I think what we mean is storing amperage, or storing current? I don't think capacitors store voltage, correct? Please correct me if I'm wrong. Thanks!
It's both. When the capacitor is charging or discharging there is current. When the capacitor is charged there is no current, just stored voltage
What a great explanation ,Thank you.
Thanks, and your welcome.
...so in a CDI ignition, the spark plug fires when the SCR switches the primary circuit "ON".?
I have seen other systems where the firing circuit arrangement is such that the spark plug fires on the RELEASE of the primary voltage. Does this one fire the plug on the RISE of the PRIMARY coil (thus the RISE of the secondary)? THIS MAKES SENSE--I even tried it and it works fine!
On the Rise.
....it's interesting. Top explanation was given in our homegrown Australia Electronics magazine 51 years ago and revisited in 1975. ..In conventional Kettering ignition system it is the sudden collapse of the built up magnetic field in the coil which built up in say period of ½ a millisecond collapsing in say ½ a microsecond that generates around 400 volts in primary of ignition coil ( (this phenomena for voltage boost isn't so familiar to many )) which then is instantly stepped up to around say 30 kilovolts by familiar transformer action of coil..With cdi however the 400 volts already is supplied available thus merely needs to be dumped by capacitor action across the primary instantaneously, and capacitors are very good for instantaneous dumping , a 1uf capacitor rated for at least 400 volts is plenty for high energy sparks up into very high revolutions for multi cylinder engines...Also cos it's the effect of forced voltage feed instead of magnetic collapse it turns out that the polarity of the spark is changed. The ideal is for the centre electrode to be negative cos it's hotter,, along lines of vacuum tubes,, but not a big deal . .gotta mention too maybe that in Kettering ignition that it's initially 12 volts across the primary that builds up to 400 upon magnetic collapse when ignition points break contact.
In the trigger coil, is the magnet on the rotor or in the trigger coil? having trouble understanding how pulse is making ac voltage.
Capacitors, DC and AC Current
czcams.com/video/NInt1Ss3vQ4/video.html
AC Alternating Current, for the Beginner
czcams.com/video/xVbqMFkyuXI/video.html
Transformer Basic Parts & Function
czcams.com/video/q3YhbugYjJY/video.html
Does this mean that the CDI boxes are standardized or is each one unique to the motor they fire? I'm having trouble finding a replacement for my CDI and was wondering if it could be remade easily.
I would not think this is a standard.
Could you run it from 6 or 12v dc battery? Or is AC (no current cycle through diode) necessary to enable the SCR to shut off after it has been triggered?
You may be able to run this on a battery but it would be a large design change.
Hi my friend, good video, I like to know if all kinds of pick up coils generate low voltage to excite the CDI? My engine is an RM 125 and 92, but it did not generate something voltage i think have a problem from my pick up coil, what do you think ?
VERY NICE. VERY UNDERSTANDABLE. THANK YOU.
Great informative video. I have a CDI on an older motorcycle. It only makes a spark once when I push the stop button and the rest of the time nothing.
I'm thinking either the SCR is bad or the trigger coil is bad and the stop button is actually discharging the capacitor.
That could be. Most of the time the parts that goes bad are the capacitors. Good luck.
Nicely explained
Thank you, and your welcome.
Great video!! I am going share this with my son.
If the trigger is given to the SCR not only while starting the bike, does it mean that CDI is required even for running the bike smoothly?
My motorcycle under cold conditions burps out for about 5-10 minutes past starting and switches off while the throttle is not revved (I set the idling to its best form but this still happens). Because of this fuel efficiency has severely been plummeted, do you think there might be a problem in the CDI. (I kind of related this to the CDI because my bike tremendously burps out through the silencer whenever i start).
Thanks for the demo was wondering how I could reverse engineer this and I think I can now. I have a bank of coils discharging into a network of caps. I then want to discharge these caps while effectively swapping the coils onto another bank of caps so I can charge these while discharging the other bank then swapping back to the other bank and then the whole sequence repeats. Just one query shouldnt the primary coils emf collapse as the cap discharges then induce into the secondary coil and across the spark gap?
Nice circuit animation....thanks Rick.
Muy claro, gracias. ( Very clear, thanks)
Thank you, and your welcome.
Hope this video helps.
Thanks so much for the great explanation sir.
Your welcome
Whats the resistor for? And what would it's rating be? Is to stop current from the trigger or is it to stop current from the charging magnet?
The resistor is to keep from over driving the gate.
Good video and explanation but the one thing that I feel is missing is an explanation of how the collapsing magnetic field in the primary winding relates to a spark being generated.
Transformer Basic Parts & Function
czcams.com/video/q3YhbugYjJY/video.html
Transformers, a few basics
czcams.com/video/UvHCQswnjEg/video.html
Impedance, Back EMF, AC Resistance
czcams.com/video/y11SbmXPY18/video.html
Recall that primary and secondary are wound on the same core. A sudden drop in the primary's magnetic field produces the same drop in the secondary's field. Thus the secondary's terminals develop a voltage across them that is proportional to the rate of change of the magnetic field.
Do you really need a diode in the ignition stop switch?
It does half the current through the Excitor Coil. That should extend the life of the coil.