$20 LCR ESR Transistor checker project

[madires]

I have a question - whether it is possible to add an inductance icon on the display on the right how it is made for transistors or thyristors? 

Yes, it's possible. It could be done by using LCD_FancySemiPinout(), but the the symbol would waste flash memory (just a rectangular region inside a square, 50% wasted). Another approach would be to add rectangular symbols for 2-pin components (more efficient) and a display function for that.

[indman]

Madires, thanks for the response! It would be excellent if you added a feature for show of icons with 2 pin components in the following revision of a firmware! 

[technogeeky]

I am getting consistently incorrect results with my GMA328 unit. All capacitor results seem to be systematically low. For instance, my known > 100 nF test capacitor was about 202 nF. The GMA328 always reports about 160 nF. Other capacitors seem to have the same systematic error. In addition, inductors seem to be systematically low. I measured a bunch of inductors of unknown value, and nearly all of them read 0.1uH or whatever the minimum value is, or just read as a resistor. Resistors seem to measure correctly.

Self-test and the more complete self-test do not seem to change this behavior.

Is there any way to investigate this further? The main difference between the schematic and my unit are that the transistors are all cheap versions of the original (e.g. they use 9014, 9012, etc). The voltage reference is a TL431. I don't have any ZIF socket or anything; I am going straight into three 22AWG silicone test leads. They are somewhat long (10 inches or so), but I calibrated that into the self-test.

The fuse configuration seems correct.

[madires]

8 or 16 MHz? Which 5V regulator?

[technogeeky]

8 or 16 MHz? Which 5V regulator?

8 MHz. 1550. The fuses appear correct.

[madires]

Could be something like a clock or comparator issue.

[casinada]

Question:
I compiled Version 1.28m AY-AT Color and enabled the External reference. The Selftest or Show Values show Vref=1088 and not my entered Value of 2498.
Am I missing something?
*
 *  2.5V voltage reference for Vcc check
 *  - default pin: PC4 (ATmega 328)
 *  - should be at least 10 times more precise than the voltage regulator
 *  - see TP_REF for port pin (config-<MCU>.h)
 *  - uncomment to enable and also adjust UREF_25 below for your voltage
 *    reference
 */
#define HW_REF25
/*
 *  Typical voltage of 2.5V voltage reference (in mV)
 *  - see datasheet of the voltage reference
 *  - or use >= 5.5 digit DMM to measure the voltage
 */
#define UREF_25           2498

Also when I place a short between Pins 1 and 2 it measures 0 ohms  , when I place a short between Pins 2 and 3 it measures 0 ohms  but when I place a short between pins 1 and 3 it measures 20pf between pins 2 and 3.

I changed the Crystal to 20MHz   

[indman]

Is there any way to investigate this further?

Show results of the T1-T7 tests

[madires]

Question:
I compiled Version 1.28m AY-AT Color and enabled the External reference. The Selftest or Show Values show Vref=1088 and not my entered Value of 2498.
Am I missing something?

Vref is the MCU's internal bandgap reference (around 1.1V).

Also when I place a short between Pins 1 and 2 it measures 0 ohms  , when I place a short between Pins 2 and 3 it measures 0 ohms  but when I place a short between pins 1 and 3 it measures 20pf between pins 2 and 3.

The resistor check looks for a resistor in both directions. If the measurements of both directions differ too much the firmware assumes that there's something wrong. The capacitor check is run afterwards. In most cases a missed low value resistor is caused by a bad connection. Wiggle the leads a little bit and try again.

BTW, how do you power the tester?

[casinada]

I tried with both a 9V battery and a battery eliminator (power supply with a 9V battery connector).
I assumed that when the external reference is enabled, vref would be the external reference shown.
Is it possible to enable and disable the reference by software to be able to compare them instead of having to recompile the firmware? 

[madires]

Ok! I've asked because sometimes a SMPSU might cause some issue. The external reference is used to get the offset of Vcc (5V). That's the reason why the reference should be more accurate (an order of magnitude) than the voltage regulator, and why its "fixed" voltage isn't displayed. The external reference is used when  HW_REF25 is set and the firmware detects a voltage around 2.5V. So you could also program using solder Adding a menu function and some control logic for a software switch should be straight forward. Be my guest

[perieanuo]

I tried with both a 9V battery and a battery eliminator (power supply with a 9V battery connector).
I assumed that when the external reference is enabled, vref would be the external reference shown.
Is it possible to enable and disable the reference by software to be able to compare them instead of having to recompile the firmware? 

Off course no,you have to recompile


Envoyé de mon iPad en utilisant Tapatalk

[madires]

Just soldered a display adapter board for an ILI9342 based display with touch screen Let's see if I'm able to add touch screen support to the firmware.

[casinada]

I haven't programmed seriously for 20 years but I'm becoming dangerous again daily 
Is it possible that with the 20MHz crystal the tester has hard time measuring resistance lower than 0.1 ohms? It has not problem detecting the shorts for calibration. 
I will go to a 16MHz crystal so I can test the K versions of the firmware as well (I prefer the m version)   

[johwaa]

I'm working on a version of the board that drives a couple of relays connected to PC3 and PD5 (which weren't used in the version of the board that I purchased). For some reason, PC3 wants to come on regardless of what I am doing with it. Is it being driven in the assembler code?

Thanks!

[madires]

I haven't programmed seriously for 20 years but I'm becoming dangerous again daily 

Duck and cover? 

Is it possible that with the 20MHz crystal the tester has hard time measuring resistance lower than 0.1 ohms? It has not problem detecting the shorts for calibration. 

I haven't noticed anything like that, but I'll check a few resistors.

[madires]

I'm working on a version of the board that drives a couple of relays connected to PC3 and PD5 (which weren't used in the version of the board that I purchased). For some reason, PC3 wants to come on regardless of what I am doing with it. Is it being driven in the assembler code?

PC3 is the analog inut for the Zener or external voltage option for an ATmega328 based tester. If that option isn't enabled in the firmware, the pin should be in HiZ mode. Which firmware are you using?

[johwaa]

I'm working on a version of the board that drives a couple of relays connected to PC3 and PD5 (which weren't used in the version of the board that I purchased). For some reason, PC3 wants to come on regardless of what I am doing with it. Is it being driven in the assembler code?

PC3 is the analog inut for the Zener or external voltage option for an ATmega328 based tester. If that option isn't enabled in the firmware, the pin should be in HiZ mode. Which firmware are you using?

I'm using 1.27, and I noticed the Zener option and made sure that it was commented out. The version of the tester that I bought is this one:
http://www.ebay.com/itm/M328-LCD-12864-Transistor-Tester-Meter-DIY-Kit-Square-Signal-Generator-US-46CI/141767800169?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

PD5 was also unused, so I'm using it for my "Fail" relay.

I've removed the tests for inductors, transistors, and resistors in the software. All that I am looking for is capacitance.

What this version of the tester does is to check the quality of the connection of a microphone where it connects to the wiring harness in the Headliner assembly (for a car). If the capacitor is between 100 micro-farads and 200 micro-farads I consider it a good connection. If the connection is bad, the result will be a higher capacitance, not higher resistance.

I re-created the board by hand and created a project in KiCad (with my relays) from it. From there, Hackvana made the boards for me (great resource!). I've built one board, and it works fine with the exception of the relays. It's just that the pesky relay off of PC3 keeps coming on.

I can post the code and the KiCad schematic now, the PCB layout will have to wait until I fix the footprints for most of the components (I got them wrong and the resistors and most of the capacitors don't fit correctly, once I fix it, I can post that too).

[pepe10000]

Is it possible that with the 20MHz crystal the tester has hard time measuring resistance lower than 0.1 ohms? It has not problem detecting the shorts for calibration. 

I haven't noticed anything like that, but I'll check a few resistors.

The same thing happens to me in the LCR-T4-H and in the AY-AT.

In resistors less than 1 Ohm indicates missing component or marks a few picofarads.

A greeting.

P.S. In both I have installed 16 Mhz quartz crystals.

[madires]

I re-created the board by hand and created a project in KiCad (with my relays) from it. From there, Hackvana made the boards for me (great resource!). I've built one board, and it works fine with the exception of the relays. It's just that the pesky relay off of PC3 keeps coming on.

How do you drive the relays?

[madires]

The same thing happens to me in the LCR-T4-H and in the AY-AT.

In resistors less than 1 Ohm indicates missing component or marks a few picofarads.

A greeting.

P.S. In both I have installed 16 Mhz quartz crystals.

I've put it on my to-do list. A quick check with a 20 MHz tester and resistors < 0.1 Ohms confirms the issue.

[madires]

For AY-AT(20MHz crystall) of a clone I changed settings of the inductor.c file. Also the enkoder works with the "define ENCODER_PULSES 2" setup better.

Could you please try "ENCODER_PULSES 4"?

[johwaa]

I re-created the board by hand and created a project in KiCad (with my relays) from it. From there, Hackvana made the boards for me (great resource!). I've built one board, and it works fine with the exception of the relays. It's just that the pesky relay off of PC3 keeps coming on.

How do you drive the relays?

The Atmega pins drive a transistor which in turn drives the relays.

[madires]

The Atmega pins drive a transistor which in turn drives the relays.

NPN with base resistor?

[pepe10000]

For AY-AT(20MHz crystall) of a clone I changed settings of the inductor.c file. Also the enkoder works with the "define ENCODER_PULSES 2" setup better.

Could you please try "ENCODER_PULSES 4"?

I tested on an AY-AT with quartz crystal of 16 Mhz with ENCODER_PULSES 4 and I noticed that it is better with ENCODER_PULSES 2.

A greeting.