$20 LCR ESR Transistor checker project

[Feliciano]

At least the new T7 has an SS210 for the HV diode that used to burn on the traditional TC-1 and clones. And I also notice the new power/timer MCU has its own crystal, and the battery arrived charged. So I'll study this design a bit to see whether it's a real improvement, or basically a workaround.

Just to check: if the last line on the 324pa is "2120G1P" means manufactured in 2021, right?

[madires]

Yep, year 2021, week 20, lot G1P.

[Feliciano]

Preliminar findings  :
On the old model (unmodified STC15, powered on when connecting the battery) there is a whine noise and high current when using not_so_low shunt. When using the lowest shunt, it registers around 280mA under functioning and 0.24mA during standby.
On the new model (new power MCU, powered off when connecting the battery) the circuit uses around 200mA when working (no whine with the DMM), and 3.6µA during standby.

So, somebody made some improvements. Perhaps read this thread? 

The main catch is still using a 324pa. Looking forward for the 64k version.

[ricktendo]

Will somebody be so kind as to share your mega328_color_kit 16MHz Makefile with me, trying to get it under 90KB with as much features as possible.

[eti]

I have the standard one, orange solder resist, mint green backlit dot matrix display:

# Why do some LEDs only show as capacitors?

# Why do small inductors (20-90uH) only show as resistors?

Thanks

[rsjsouza]

If the LED forward voltage is too high, the diode part will be an open circuit and the capacitance will be dominant. The tester will measure that.

When a very small inductor is measured in low frequency, its series resistance will be dominant. The tester will measure that.

[indman]

Why do small inductors (20-90uH) only show as resistors?

Install the latest K-firmware or M-firmware on your device and you can measure fine inductances from 50-100nH(NanoHenry) accurately enough.

[madires]

The normal inductance measurement of the OSHW firmwares can measure down to 20 or 10 µH when the tester/clone doesn't cheap out on components. The firmware measures inductance only after a resistance is detected. If the inductance measurement fails the tester assumes that the DUT is a resistor. The k-firmware supports an additional measurement method for low value capacitors and coils, called SamplingADC (requires a small reference cap in parallel with the coil). And the m-firmware supports an optional LC meter frontend (similar to the PIC based LC meters) to measure down to fF and nH.

[madires]

As promised a few pages back, here are some inverted_color_numbers [1,2,3] bitmaps to be integrated on next releases as an optional way for enhanced readability of the components_pins displayed (on ctesters with enough memory).

EDIT: Currently developed: 6x8, 8x8, 10x16, and 12x16 (all hf).

That's going to be UI_PROBE_REVERSED in the next version. If you like to create the character bitmaps for the other fonts too, be my guest.

[Feliciano]

So far I only have figured out the encoding of the hf fonts. I haven't invested so much time on the other types of fonts. If there is any other hf pending let me know, as I developed a pseudo-automatic method for reversing the colors of those.

[madires]

I've converted your 'hf' bitmaps for 6x8, 8x8, 10x16 and 12x16 into the other formats of the same sizes. Other fonts in 'hf' format are font_16x26_hf.h and font_8x16_win1251_hf.h.

[eti]

If the LED forward voltage is too high, the diode part will be an open circuit and the capacitance will be dominant. The tester will measure that.

When a very small inductor is measured in low frequency, its series resistance will be dominant. The tester will measure that.

But the led lights up

[Yuriy_K]

But the led lights up

You can show an image on your display or write what is not shown. My example :

[madires]

The diode check is a little bit more complex than you might think. Several measurements are done to filter out other components which exhibit similar behaviour. There can be fringe cases in which a filter fails and the DUT is wrongly dedected as a diode or vice versa. For example, one of those filters checks if the forward voltage is between 0.15 and 4.64 V.

[Feliciano]

That's going to be UI_PROBE_REVERSED in the next version. If you like to create the character bitmaps for the other fonts too, be my guest.

Here, the reversed_colors [1,2,3] numbers of the horizontally_flipped bitmaps, to be integrated on next releases as an optional feature for enhancing readability of the components_pins displayed on ctesters with enough memory for this. I also attach a sample of how I imagine it would look like on a monochrome display.

[indman]

I would remove the circle from the element images. On a low resolution display, these circles are distorted and look clumsy.Still, they don't carry any useful information.

[madires]

You've got a point there!

[Feliciano]

I would remove the circle from the element images. On a low resolution display, these circles are distorted and look clumsy.Still, they don't carry any useful information.

Do you mean the circle around some symbols?
The icons of my previous picture are the 30x32. There is also the 24x24 and 32x32 (I haven't rendered those). For low_res displays it's very importante to balance the font_size and the symbol_size. As you suggest, the circle could be removed, and the size of the symbol be increased. This could be pondered and added as an option too

[indman]

Do you mean the circle around some symbols?

Yes.

[carrascoso]

Hi all.
I am testing the new features of the firm v1.45m on a GM328 color kit.
But there are some functions that do not appear in the menu, I do not know if they should really appear in it or not.
#define HW_BUZZER, this function does not appear in the menu, I understand that without appearing it would work having the meter modified with a buzzer, a modification that I will make shortly.
#define UI_THREE_PROFILES, this other one does not appear in the menu, besides not knowing what use it has.
I would ask for a little guidance on it.
Thanks

[madires]

HW_BUZZER is a simple hardware option which is used by SW_CONTINUITY_CHECK. It's kept separate because other functions might use it in the future too. UI_THREE_PROFILES adds a '#3' to the load/save menus.

[TERRA Operative]

Question for the gurus here..

I have an LCR-T4-H (Green backlit monochrome display, yellow solder mask) that shows 'MTester v2.68 by Efan & HaoQixin/91make.taobao.com' on the initial screen.

Does anyone know of a newer firmware for this unit?

[madires]

The latest OSHW firmwares: k-firmware 1.13k or m-firmware 1.45m

[madires]

I would remove the circle from the element images. On a low resolution display, these circles are distorted and look clumsy.Still, they don't carry any useful information.

What do you think about adding small pin designators, like B, C and E for a BJT?

[indman]

This is convenient, fast and clear, of course, as long as these small symbols are distinguishable on the different types of displays.
Will this be in addition to numbers 1-2-3 or instead of them?