$20 LCR ESR Transistor checker project

[SteveM]

That ebay seller messed up when attempting to label that picture.  The center button is actually two buttons.  The top half is on/test and the bottom half is off.  The three buttons to the right are something completely new.

[iloveelectronics]

They must be re-using a case with completely different purpose...

The sockets and buttons are labelled as "send message", "volume/lookup", "menu/confirm", "dial", "shortcut" etc. And the device is labelled "Chinese SMS Sender" or something. Completely unrelated to ESR 

[Rerouter]

Time to put my foot in with this project

Just bought one of these, (hope i picked correctly)
http://www.ebay.com.au/itm/200960094152?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[neslekkim]

That ebay seller messed up when attempting to label that picture.  The center button is actually two buttons.  The top half is on/test and the bottom half is off.  The three buttons to the right are something completely new.

I thought those two buttons in the center would be for some paging in the display..
but the standard firmware is not supporting that type of screen ?, much bigger symbols, and also chinese text inside.

[SteveM]

Thank you all for the replies and thank you iloveelectronics for the translation.  That is very puzzling.  I would think it wouldn't take much to manufacture their own plastic box and label it correctly.

[madires]

Just bought one of these, (hope i picked correctly)
http://www.ebay.com.au/itm/200960094152?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

It's one of the standard clones with an ATmega328. Might need an ISP header for firmware updates.

[neslekkim]

It's one of the standard clones with an ATmega328. Might need an ISP header for firmware updates.

Have you seen those with the bigger screen, is that something that is supported in the firmware now?, or is that an custom chinese hack?

[madires]

I thought those two buttons in the center would be for some paging in the display..
but the standard firmware is not supporting that type of screen ?, much bigger symbols, and also chinese text inside.

It has to be a custom modification to support that LCD and include the extra symbols. Unfortunately the vendor doesn't seem to care about the project's Open Source Hardware nature.

BTW: A small Russian company will offer a transistortester clone with a nice enclosure (with pads for SMD, contacts for through-hole stuff and test clips) soon.

[madires]

Thank you all for the replies and thank you iloveelectronics for the translation.  That is very puzzling.  I would think it wouldn't take much to manufacture their own plastic box and label it correctly.

Could be less expensive than manufacturing new boxes. We don't know how much the vendor pays for those boxes and LCDs. But I don't recommend to buy any of those testers because they obviously don't run the "official" firmware. So you would be stuck with the firmware version installed.

[neslekkim]

I thought those two buttons in the center would be for some paging in the display..
but the standard firmware is not supporting that type of screen ?, much bigger symbols, and also chinese text inside.

It has to be a custom modification to support that LCD and include the extra symbols. Unfortunately the vendor doesn't seem to care about the project's Open Source Hardware nature.

BTW: A small Russian company will offer a transistortester clone with a nice enclosure (with pads for SMD, contacts for through-hole stuff and test clips) soon.

Cool, will that one also include programming headers/port etc?

[madires]

BTW: A small Russian company will offer a transistortester clone with a nice enclosure (with pads for SMD, contacts for through-hole stuff and test clips) soon.

Cool, will that one also include programming headers/port etc?

If I got that right it has a 10 pin ISP header (unpopulated).

[amtpdb]

How long before it is being sold? Where will it be sold and for how much? What will it be able to do and how well? I need an esr meter.
 Thanks for any reply.

[madires]

How long before it is being sold? Where will it be sold and for how much? What will it be able to do and how well? I need an esr meter.

Got no idea about the date or price but they already offer ESR meters (http://www.radiodevices.ru/).

[amtpdb]

OK Thanks for responding.
Don

[Gandalf_Sr]

Mine has arrived.  Not done much with it yet but it works and appears reasonably accurate.

One aspect that's not as good as I thought is the ZIF socket.  It says 3M on it although it's probably a cheap Chinese copy; the issue is that it's about 5 mm from the top of the socket to where the actual connections start so testing a through-hole component that's been removed from a PCB would be almost impossible.  If I do a redesign, I'll go with the machined 0.1 pitch sockets + the SMT pads.

[J-D-H]

I bought one of these tester via eBay, but the LCD display does not seem to have back-lighting.  The tester's main PC board is labeled "Ver 2.4 2013/07/01"; the PC board holding the LCD display is labeled "Zijing Electronics".  Pads 15 and 16 on the display PC board are unused (no pins attached), but these two solder pads do have traces connected to them (hard to trace the connections -- no schematic, solder mask, etc.).  Does anyone know whether back-lighting on this tester's LCD module can be enabled?  If so, how?  Also, would the 25-50mA or so for the back-light LEDs be too much for the 5V regulator?  Any help would be appreciated!

John

[Rerouter]

JHD, look between the LCD and its board, if there is a gap it has no back-light installed, if it has something white and about 1mm thick in the way it is installed but not powered,

now if its a generic LCD there is generally a set of jumpers on the back and pads for a dropping resistor to power the back-light off the VCC rail

[madires]

I bought one of these tester via eBay, but the LCD display does not seem to have back-lighting.  The tester's main PC board is labeled "Ver 2.4 2013/07/01"; the PC board holding the LCD display is labeled "Zijing Electronics".  Pads 15 and 16 on the display PC board are unused (no pins attached), but these two solder pads do have traces connected to them (hard to trace the connections -- no schematic, solder mask, etc.).  Does anyone know whether back-lighting on this tester's LCD module can be enabled?  If so, how?  Also, would the 25-50mA or so for the back-light LEDs be too much for the 5V regulator?  Any help would be appreciated!

The first thing is to check if the LCD module has a backlight. Apply some mA to pads 15 and 16 and see if something happens. Use a PSU or a battery with a resistor to limit the current. The voltage regulator doesn't matter much. If it's able to provide enough current to power the backlight also you could simply add a resistor in series with the backlight. If not, build a small PWM backlight control with a current limiter, power the PWM by the 5V regulator and power the backlight by the battery directly (via a MOSFET with the current limiter). Or use some special LED driver (DC-DC converter, regulated by current).

[J-D-H]

JHD, look between the LCD and its board, if there is a gap it has no back-light installed, if it has something white and about 1mm thick in the way it is installed but not powered,

now if its a generic LCD there is generally a set of jumpers on the back and pads for a dropping resistor to power the back-light off the VCC rail

Thanks for the quick and clear info!  I hoped the display might be internally edge lit, but if the BL function is always done with discrete LED(s), I'm out of luck -- mine has none visible.  I'm thinking of trying to tack a lead to the 5v switched voltage someplace and then using this to power a couple of flat style LEDs wedged under the LCD (shaving the LED thickness as needed).  Having a BL when the circuit is working sounds like a nice idea.  However given the fairly small A-hr capacity of 9V batteries, it might be best to just forget the whole idea.....

[J-D-H]

The first thing is to check if the LCD module has a backlight. Apply some mA to pads 15 and 16 and see if something happens. Use a PSU or a battery with a resistor to limit the current. The voltage regulator doesn't matter much. If it's able to provide enough current to power the backlight also you could simply add a resistor in series with the backlight. If not, build a small PWM backlight control with a current limiter, power the PWM by the 5V regulator and power the backlight by the battery directly (via a MOSFET with the current limiter). Or use some special LED driver (DC-DC converter, regulated by current).

Thanks for your ideas!  If I understand correctly that back lighting of these LCD display modules is usually done via discrete LEDs, I see none behind mine.  I'll think about the idea of adding this function (as you suggested).  My first thought is to just use two LEDs in series via a simple dropping resistor to Vcc -- time for some experiments to see whether this sort of BL looks acceptable or not.....

[paulie]

i can tell you none of the low cost ebay units have backlight. aside from cost issues the 9v battery life would be severely impacted. since i converted mine to 5vdc this was not an issue so swapping with a backlit unit was practical. trying to upgrade a non-lit one is not possible. theres more involved than just popping leds behind it. and why bother with lit units available for 2 bucks (shipped):

http://www.ebay.com/itm/LCD-Display-Character-Module-LCM-16x2-HD4478Controller-Blue-Blacklight-1602-TR-/181271994104?pt=LH_DefaultDomain_0&hash=item2a34a71ef8

ill also mention asking the seller for details is another exercise in futility. mine swore it was backlit and used m328 not m8. both turned out not to be true. however for $10 i wasnt about to open a case. i will say the m8 version dont hold a candle up to the m328 hex file that markus posted here. no inductance, no calibration, etc and unbelievable spelling errors. since i built diy versions with serial io for less than a buck that work better i regret ordering that ebay one. live and learn.

[Rerouter]

a few pages back i posted a link to the one i purchased and it came with a back-light and the 328 mega in it, just missing an isp header,

[J-D-H]

i can tell you none of the low cost ebay units have backlight. aside from cost issues the 9v battery life would be severely impacted. since i converted mine to 5vdc this was not an issue so swapping with a backlit unit was practical. trying to upgrade a non-lit one is not possible. theres more involved than just popping leds behind it. and why bother with lit units available for 2 bucks (shipped):

http://www.ebay.com/itm/LCD-Display-Character-Module-LCM-16x2-HD4478Controller-Blue-Blacklight-1602-TR-/181271994104?pt=LH_DefaultDomain_0&hash=item2a34a71ef8

ill also mention asking the seller for details is another exercise in futility. mine swore it was backlit and used m328 not m8. both turned out not to be true. however for $10 i wasnt about to open a case. i will say the m8 version dont hold a candle up to the m328 hex file that markus posted here. no inductance, no calibration, etc and unbelievable spelling errors. since i built diy versions with serial io for less than a buck that work better i regret ordering that ebay one. live and learn.

On adding back lighting, a simple test with a light source held near the edge of the LCD module seems to indicate that adding a couple of small LEDs might do the trick.  But a new LCD module complete with BL would be easier -- thanks for the link!  Maybe I'll get one of these, but first I'm going to think over the topic of battery drain.  That, and make some measurements to see whether my tester board's pins 15 and 16 are actually connected to anything.  BTW, I did think about contacting the seller and asking about the BL, but guessing the result, I didn't try <g>.

[J-D-H]

a few pages back i posted a link to the one i purchased and it came with a back-light and the 328 mega in it, just missing an isp header,

I'll look back and try to find the link.  Thanks.

[paulie]

a few pages back i posted a link to the one i purchased and it came with a back-light and the 328 mega in it, just missing an isp header,

yes, the more costly ones do come with m328 and backlight as mentioned in the listings for those. unfortunately low cost units like mine ($10 bo, $15 bin) cut corners in both categories.  what annoyed me was the seller did not tell the truth about that. pretty good deal though considering and only took me a couple minutes to upgrade mcu and display.

and its true you can put leds behind a non lit unit but there are factors like diffuser and different polarizing screen that degrade visibility so much its not worth it. i should also mention that the yellow/green backlight appears much brighter than the blue ones. at least to my eyes.