This really has me thinking about some disappointing results I've had with different projects through the years and me thinking I was saving money on some component purchases. I think I'm going downstairs and sorting through my parts cabinet.
As I noted with the previous video, the 2 volt dropout voltage from the datasheet is the "typical" value and specified at 1.0 A output. Using "typical" values is unsafe. No maximum value appears in the tabular specs. From the datasheet _Figure 30. Peak output current vs input/output differential voltage_ is helpful though hard to read in the area of interest. It does show that at moderate die temperature something above 2.0 V input-output differential is required for 1.5 A output current. In one video I watched recently a bunch of op amps were tested for slew rate. One of the best performers was marked as an LM324. The slew rate of a genuine 324 is mediocre at best. In another video signal applied to the inverting input was showing up on the non-inverting input, though the measurements were crude and didn't really provide good information. In any case, that should not happen in the circuit that was used (amp run open-loop as a comparator). In both cases the parts were from other than authorized distributors. It seems there is a lot of counterfeit junk being sold. It seems that you can get lots of grief cheaply. === Why dropout would be higher for higher output current: The output stage is a darlington pair as an emitter follower. Current gain won't be uniform over the full load current range and typically starts to drop as current becomes "high" for the size of the transistor. That means more base current is required in each of the transistors in the pair and that means their base-emitter voltage will increase. There is also a resistor in the emitter of the main pass transistor and its voltage will be linearly proportional to load current. The Vbe drops and sense resistor drops all play into the dropout voltage requirement. Vbe has an inverse relationship with temperature, so the dropout voltage declines as the IC gets hotter. Figure 29 in the datasheet shows how typical dropout voltage varies with "junction" temperature (meaning the actual IC "die" temperature).
Adafruit is basically America's AliExpress outlet shop.. so I'm totally not surprised that they're bringing Chinese counterfeit chips into the supply chain. I hope you notified Mouser and/or Adafruit about those shady parts. Please post an update if/when they reply to that.
This is turning into a really interesting series on how to spot a dodgy LRO. Can you do a video showing how you made the load jig? It seems like it could be a fun weekend project. :)
wow.. so surprised at this update. Right after your previous tests on the 7805, I purchased some from Mouser to replace the ones I had purchased on Ebay or Aliexpress (I can't remember where i got them). Luckily, the ones I got from Mouser were STM... not the adafruit.
That's interesting. 7805s should have a drop out of around 3V, so 5V + 3V = 8V should remain close to 5V hold on 1.5A. The 7V in, 5V out was going to be a bit dodgy, even with the legit chip. But not as dodgy as that Adafruit one. Pretty good demo!
I also need to test my bojack electrolytic capacitor kit. Those were reading right capacitance but I'm sure you can't use them at rated voltage or their ESR is way off. Need to do test jig with current limit resistor that I don't have that paper stuff all over my room when they normally would explode. At least one cap was "leaking". It had hard white stuff where the leads are. Normally you left some safety margin for rated values so they may be fine for test purposes but not for longtime use.
@@LimbaZero The pack of inductors I bought has insane ESR. Totally unusable. But they do ballpark their rated inductance values so I guess it's on me for not asking if they're functionally useless despite being sold as electrical components along side other electrical components found when shopping for electrical components.
@@nathanieljames7462 If inductor looks like resistors then those are usually used to filters and maybe filters between powers planes/rails. Also quickly checked datasheet from mouser from other style inductors (radial with heat shrink) they are "ok" for up to 250 kHz smps. New chips seems to require fully closed ferrite inductors. Basically all kits are old tech if not counterfeit. Edit: you can basically search that certain size inductor from mouser and check if picture looks same then download datasheet and verify if it's far away of those parameters.
honestly i love those videos becase i also got scamed on bd244's and ams 1117 and it is very annoying to replace part that worked for 20 years no problem and got damaged by accident to the same part that don't even last one power cycle and think if it is you or the part that broken :] so thank you for fighting nonbelivers and showing exactly what isgoing on by the way some sellers claim that oryginal regulator is 500 or 800mA only to avoid returns which is very borderline
thankfully, the only times I ever used off brand 7805's was for things it realy didn't matter for (like display back light LED mods). anything more involved, it was always the genuine parts for many reasons and I verified that what I got was within spec for the parts. I honestly had no idea the off-brand regulators was so bad, wow.
Nothing new when dealing with Adafruit, happened at least three times on different components. I suspect that they got bitten during the component shortage these last couple of years and are just passing the bad parts along to unsuspecting hobbyists instead of binning them like they should.
Wouldn't the max response be: "just shut down your project and remove the component, ship it to us and we will send you another crappy replacement."@@DCFluX
one more thing, i know it is pointless to use a regulator this way but sometimes it is required to get linear regulation working from way higher voltage than +2v above what you want out and those ic's are rated up to 34v if i am remembering corectly i have no idea how hot would 7805 get powering 1,5a from that voltage, probably a lot but 15-16v should be totaly acceptable so there is a test for a real ic and a fake ic how high can a voltage go before the ic burns up and does any of then thermal runaway or shootdown because loosing avoltage regulator is nothing, loosing a whole project because of bad regulator is another story and what to do with high voltage differences push current trough cascading regulators of different values?
You do not follow the data sheet specification regarding the capacitors. Since the beginning of the 78xx era all data sheet saying: Input 0,33 uF and at the output 0,1 uF. Other values are not required and do not fit the needs of the regulator.
It's frustrating that reputable sellers are also trying to become "marketplaces" as well, allowing unreliable re-sellers to sneak into their catalogue. Another slightly related trend is always showing something in search results, even if it's not really related to what you're searching. If you don't have part - just show "Nothing found" ffs.
wow someones raided the reject bin! interesting that with the china marking youd expect them all to be reject/fake , and genuine to be from tailand ,philipeans ,korea, hong kong but if only it were that simple
This video shows that even reputable electronic components suppliers can sell different quality parts due to their manufacturers and other sourcing roots ... But in the end you may not fall into disasterious components performance like from anonymous suppliers on the web ... As my experience with anonymous suppliers , not all of them are willing to cheat you BUT YOU ARE THE ONE WHO WAS CHEATING YOUR SELF so RESPECT YOURSELF AND DON"T RUN AFTER CHEAPER PRICES LIKE A DOG and DON"T EVEN BARGAIN ON SOMETHING YOU CAN PAY EASILY just to fulfil your greediness !!...
Great work. Good reason to always salvage 78XX regulators from trashed products. They can be trusted to be genuine OEM components and not fake.
This really has me thinking about some disappointing results I've had with different projects through the years and me thinking I was saving money on some component purchases.
I think I'm going downstairs and sorting through my parts cabinet.
As I noted with the previous video, the 2 volt dropout voltage from the datasheet is the "typical" value and specified at 1.0 A output. Using "typical" values is unsafe. No maximum value appears in the tabular specs.
From the datasheet _Figure 30. Peak output current vs input/output differential voltage_ is helpful though hard to read in the area of interest. It does show that at moderate die temperature something above 2.0 V input-output differential is required for 1.5 A output current.
In one video I watched recently a bunch of op amps were tested for slew rate. One of the best performers was marked as an LM324. The slew rate of a genuine 324 is mediocre at best. In another video signal applied to the inverting input was showing up on the non-inverting input, though the measurements were crude and didn't really provide good information. In any case, that should not happen in the circuit that was used (amp run open-loop as a comparator).
In both cases the parts were from other than authorized distributors. It seems there is a lot of counterfeit junk being sold. It seems that you can get lots of grief cheaply.
===
Why dropout would be higher for higher output current:
The output stage is a darlington pair as an emitter follower. Current gain won't be uniform over the full load current range and typically starts to drop as current becomes "high" for the size of the transistor. That means more base current is required in each of the transistors in the pair and that means their base-emitter voltage will increase. There is also a resistor in the emitter of the main pass transistor and its voltage will be linearly proportional to load current. The Vbe drops and sense resistor drops all play into the dropout voltage requirement. Vbe has an inverse relationship with temperature, so the dropout voltage declines as the IC gets hotter. Figure 29 in the datasheet shows how typical dropout voltage varies with "junction" temperature (meaning the actual IC "die" temperature).
Adafruit is basically America's AliExpress outlet shop.. so I'm totally not surprised that they're bringing Chinese counterfeit chips into the supply chain. I hope you notified Mouser and/or Adafruit about those shady parts. Please post an update if/when they reply to that.
This is turning into a really interesting series on how to spot a dodgy LRO. Can you do a video showing how you made the load jig? It seems like it could be a fun weekend project. :)
This video is awesome! Thanks for the tips and advice 😌
Glad it was helpful!
wow.. so surprised at this update. Right after your previous tests on the 7805, I purchased some from Mouser to replace the ones I had purchased on Ebay or Aliexpress (I can't remember where i got them). Luckily, the ones I got from Mouser were STM... not the adafruit.
That's interesting. 7805s should have a drop out of around 3V, so 5V + 3V = 8V should remain close to 5V hold on 1.5A. The 7V in, 5V out was going to be a bit dodgy, even with the legit chip. But not as dodgy as that Adafruit one. Pretty good demo!
I knew what the outcome would be, And I always been buying the quality parts too
The legit ones are way less in q of 10@ .569 vs .75 each for the questionable one . Well that made it easy .
Very nice test! Thanks for the °C conversion, when you said 69 degrees like ambien I got worried I was watching a lizardmen.
I've been testing all my componwnts from Amazon and it's all fake. Even the resistors ffs
I also need to test my bojack electrolytic capacitor kit. Those were reading right capacitance but I'm sure you can't use them at rated voltage or their ESR is way off. Need to do test jig with current limit resistor that I don't have that paper stuff all over my room when they normally would explode.
At least one cap was "leaking". It had hard white stuff where the leads are.
Normally you left some safety margin for rated values so they may be fine for test purposes but not for longtime use.
@@LimbaZero The pack of inductors I bought has insane ESR. Totally unusable. But they do ballpark their rated inductance values so I guess it's on me for not asking if they're functionally useless despite being sold as electrical components along side other electrical components found when shopping for electrical components.
@@nathanieljames7462 If inductor looks like resistors then those are usually used to filters and maybe filters between powers planes/rails.
Also quickly checked datasheet from mouser from other style inductors (radial with heat shrink) they are "ok" for up to 250 kHz smps. New chips seems to require fully closed ferrite inductors. Basically all kits are old tech if not counterfeit.
Edit: you can basically search that certain size inductor from mouser and check if picture looks same then download datasheet and verify if it's far away of those parameters.
honestly i love those videos becase i also got scamed on bd244's and ams 1117 and it is very annoying to replace part that worked for 20 years no problem and got damaged by accident to the same part that don't even last one power cycle and think if it is you or the part that broken :]
so thank you for fighting nonbelivers and showing exactly what isgoing on
by the way some sellers claim that oryginal regulator is 500 or 800mA only to avoid returns which is very borderline
thankfully, the only times I ever used off brand 7805's was for things it realy didn't matter for (like display back light LED mods). anything more involved, it was always the genuine parts for many reasons and I verified that what I got was within spec for the parts. I honestly had no idea the off-brand regulators was so bad, wow.
Shame on Mouser! I always assumed I was getting legit parts from them. Chinesium is everywhere.
Nothing new when dealing with Adafruit, happened at least three times on different components. I suspect that they got bitten during the component shortage these last couple of years and are just passing the bad parts along to unsuspecting hobbyists instead of binning them like they should.
Have you contacted Adafruit about the issue?
No.
Wouldn't the max response be: "just shut down your project and remove the component, ship it to us and we will send you another crappy replacement."@@DCFluX
Priority 1 ??? Why do I always get priority 2 when ordering from Mouser????? (not that I know what the difference is :-)
Hmm, did You ever try probing the output with the oszilloscope? Just in case if there is any oscillation going on...
I always pronounced it mouse-er instead of mowz-er. Too late for me to change now. LOL
one more thing, i know it is pointless to use a regulator this way but sometimes it is required to get linear regulation working from way higher voltage than +2v above what you want out and those ic's are rated up to 34v if i am remembering corectly i have no idea how hot would 7805 get powering 1,5a from that voltage, probably a lot but 15-16v should be totaly acceptable
so there is a test for a real ic and a fake ic how high can a voltage go before the ic burns up and does any of then thermal runaway or shootdown
because loosing avoltage regulator is nothing, loosing a whole project because of bad regulator is another story
and what to do with high voltage differences push current trough cascading regulators of different values?
You do not follow the data sheet specification regarding the capacitors. Since the beginning of the 78xx era all data sheet saying: Input 0,33 uF and at the output 0,1 uF. Other values are not required and do not fit the needs of the regulator.
Labeled on package with letters CN meant that the part was manufactured in China
It's frustrating that reputable sellers are also trying to become "marketplaces" as well, allowing unreliable re-sellers to sneak into their catalogue. Another slightly related trend is always showing something in search results, even if it's not really related to what you're searching. If you don't have part - just show "Nothing found" ffs.
wow someones raided the reject bin! interesting that with the china marking youd expect them all to be reject/fake , and genuine to be from tailand ,philipeans ,korea, hong kong but if only it were that simple
Normally those boxes go straight to recycle in companies.
This video shows that even reputable electronic components suppliers can sell different quality parts due to their manufacturers and other sourcing roots ... But in the end you may not fall into disasterious components performance like from anonymous suppliers on the web ...
As my experience with anonymous suppliers , not all of them are willing to cheat you BUT YOU ARE THE ONE WHO WAS CHEATING YOUR SELF so RESPECT YOURSELF AND DON"T RUN AFTER CHEAPER PRICES LIKE A DOG and DON"T EVEN BARGAIN ON SOMETHING YOU CAN PAY EASILY just to fulfil your greediness !!...
dot... dot... DOT? DOT! POINT DAMM IT! Get consistent!