$20 LCR ESR Transistor checker project

[hapless]

Have you also programmed the EEPROM?

[ElectronicCat]

Have you also programmed the EEPROM?

D'oh, I just noticed I forgot to include it in the avrdude command. Just flashed with the ST7565_kit firmware and the display works now, although it takes a few seconds to come on, and it seems to only measure capacitors (off by a factor of 10). It doesn't seem to detect anything else and the rotary encoder doesn't seem to work very well. As soon as I manage to get into the menu it seems to turn itself off. I'll try with the other ST7565 firmware for now, unless anyone has any ideas?

[hapless]

Erm... Have you set the fuses?

[ElectronicCat]

Do they have to be set to anything in particular? I think avrdude said something about setting them automatically and I said 'yes'. Command I'm using is avrdude -P /dev/ttyUSB0 -b 19200 -c avrisp -p atmega328 -U flash:w:TransistorTester.hex -U eeprom:w:TransistorTester.eep. Also got back from testing all the firmware again, st7565_kit is the only one that give any kind of screen output.

[hapless]

At the very least, the clock needs to be redirected from internal to quartz (and its speed set according to the crystal's frequency). Try adding this to the command:
-U lfuse:w:0xf7:m -U hfuse:w:0xd9:m -U efuse:w:0xfc:m

Note: I'm pretty sure that this is safe to do. Still... Use at your own risk, and check that these values don't disable SPI programming or the RESET line. Not responsible for bricked MCUs.

[rrinker]

 Yes, you can do just the fuses - that's what I did to the 328 that came with my tester after I swapped the 8MHz crystal for a 16MHz. It wouldn't boot, I set JUST the fuses, then it would boot but naturally all cap values were off by x2 as was the output of the function gen feature.

 Rather than make 2 posts - I just installed the K firmware for my AY-AT model using the 16MHz files. I have 2 brand new 328s, first one took the Flash and EEPROM no problem, but it just would not accept the efuse setting of 0xFC. So I tried the second one - same deal. Flash writes and verifies, EEPROM writes and verifies, but it will not accept efuse 0xFC. The one that came with my tester had no problem setting efuse. A little investigation says some 328's seem picky about setting bits that aren't actually used (maybe fakes? Maybe mine are fake?). The ACTUAL fuse setting when you use 0xFC is 0x04, so I set it to 0x04, it took that. First one, I got the whole screen to light up when pressing the encoder but it wouldn't start. The second one - success. Booted up, warned that it was not calibrated, etc. Ran through the cal (the original one wanted a 1000nF, this one asks for a 100nF). Kept showing the 100nF as 59nF. But resistors were right on, and other caps like a 220uF were within tolerance. I checked more ot the 100nF's in the bag - all came up 58 or 59nF. Double You Tee Eff? I don't have any others besides an assortment of ceramics and an assortment of electrolytics - testing a few others and they were fairly close, probably within tolerance. Then I remember, the BM235 DOES have a cap tester. So I tested one of these supposed 104's - it read 59nF. So what I really have are some dodgy as capacitors. Guess that'll learn me to buy cheap Chinese assortment sets. I tried a few at random and they generally match the marked value within tolerance, just this 104's are ALL way low.
 Checked the function gen - up to the 400 and change KHz setting it's dead on per my scope, and only slightly off on the higher ones. 50, 60, and 100 are 50.00, 60.00, and 100.00. So it is the right firmware for a 16MHz crystal. Guess I need to get myself some fairly precision caps of the right values to truly calibrate it. Resistors are dead on, it detected the proper Vf for an LED I tossed on, and had no problem with an NPN BJT or an IRF540 N channel MOSFET. Looks like I have a winner. And it probably was ok with an 8MHz clock with the original firmware as well, it's those joke caps that were leading me astray.

[bitseeker]

Well, at least now you know you can have some confidence in the tester.

[tomas1808]

I am thinking about making/buying one of these.

Which chinese model is considered best and/or easy to mod to original specs?

Or should I just make my own tester using the official schematic?

Thanks!

[hapless]

How much research have you done on this? Just curious.

[ElectronicCat]

Ok, I've set just the fuse values and that seemed to fix it. The extended calibration caught me out a bit and I had to dig around for the specified capacitor values but got them eventually, and then after calibration it seemed to work fine again. Thanks for the help.

[rrinker]

Well, at least now you know you can have some confidence in the tester.

At least for resistors and capacitors. I don't have a proper transistor tester to see if the values it is giving me are accurate, but it clearly can properly distinguish types at least. I guess this means back over to the TEA thread and start looking for a transistor tester - there may be a new acronym to add to the list too, something about having at least two of everything to validate the results, and even better, three so there is a tie breaker. 

[madires]

I know what you mean. I've got more Transistor Testers than scopes. It's such a pleasure to see them all agreeing on a component

[bitseeker]

I guess this means back over to the TEA thread and start looking for a transistor tester - there may be a new acronym to add to the list too, something about having at least two of everything to validate the results, and even better, three so there is a tie breaker. 

DEEP, DMM, and TEST are related afflictions, but don't specifically define use cases. So, you might have a bit of any of them.

[tomas1808]

How much research have you done on this? Just curious.

Enough to conclude that asking would be the best way to go. I've searched for certain keywords on the print version of this thread but got nothing. It would take much less time building the thing than reading a thread the size of a small book.

I guess I was wrong about the asking part.

[bitseeker]

Tomas, the AY-AT model is one of the latest and probably most feature complete version. But it depends if you need all that. Hence, there is no single best choice for everyone.

Start reading from this post forward:

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg1156384/#msg1156384

It's significantly less than a book and will give you some recommendations from which to make a choice.

[tomas1808]

Thanks bitseeker, that's exactly what I was looking for.

I'm still considering making my own though. I will share my design if I manage to do it.

[Housedad]

so I finally got my bench, test gear, and spare parts together and went to the bench last night to play.   First thing was to take the tester (an AY-AT) and try it out on some of the Chinese spare parts to see how good/bad they were.  I have a wall wart for the power and proceeded to plug it in.   Screen lights up, dims, and the smell of blue smoke is in the air.  I quickly unplugged it, but it was too late.   I had plugged in the wrong wall wart.  It was 12VAC.  It fried the 10uf Cap which shorted the first 9012 transistor, cooking it.  I used the Microscope to see the 9012 and cap had micro bubbles on the surface.  Naked eye would never have seen it. Dmm showed shorts.  Desoldered, replaced, put the right wall wart into it, (12vDC) and it powered right up. 

I would never have guessed that the first thing I would do at that bench would be to fix my own mistake!

[bitseeker]

Well, Housedad, now that that's out of the way, onward and upward!

[hapless]

Well, if I had eyes rolling around naked on my new bench, I'd probably mix up my power supplies, too.    But if there's a danger of this happening again (and with two small power supplies that can plug into the same jack, there usually is), I would carefully break the trace from the positive lead of the socket and solder in a diode. Just in case.

[Housedad]

Good Idea.  I think I will do that soon.

[texaspyro]

I color code all my wall wart connectors with colored zip ties and put a zip-tie style cable marker with the voltage on them at the cable end.   I use a matching colored marker pen on or near the device power jacks.  It's way to easy to screw things up when you have 5/6/9/12/19/24/48 volt wall warts with 2.1mm barrel plugs on them.

[madcat]

hi,
i just bought some blank atmega328p chips to try 16mhz crystal upgrade on the AY-AT model.
does the chip programming can be done on arduino uno board with usbasp programmer?

[madires]

You can use the Arduino as ISP programmer (there's a sketch for that included in the IDE) with avrdude. usbasp is also an ISP programmer.

[ElectronicCat]

hi,
i just bought some blank atmega328p chips to try 16mhz crystal upgrade on the AY-AT model.
does the chip programming can be done on arduino uno board with usbasp programmer?

Do you mean using the Arduino as the programmer (using ArduinoISP sketch) and a breadboard or using a USBasp programmer on an arduino with a blank chip? The former is definitely possible, but you'll need a crystal oscillator set up at the same frequency on the breadboard or wherever you program it. The latter I think should also work, provided the crystal is the same frequency but I've never tried it.

[mauroh]

If I got it correctly, since the tester don't have an ICSP connector...
Yes, you can sit the Atmega in an Arduino and use the usbasp connected to the ICSP connector to flash the firmware.

Mauro