Could you please try "ENCODER_PULSES 4"?
The Atmega pins drive a transistor which in turn drives the relays.
NPN with base resistor?
I reported about a problem with determination of resistance below 0.1 Ohms also earlier. It doesn't depend on crystal frequency. The great influence is exerted by quality of test contacts and a reliable clamp of the checked detail. But even, if to satisfy these conditions, the tester determines the low-impedance resistance not always.
Sometimes two (or even more) different problems add up.
The Atmega pins drive a transistor which in turn drives the relays.
NPN with base resistor?
What's the operating freq. of the project meter as of this writing?
Where can I find the schema and BOM?
Great project idea, BTW!
What's the operating freq. of the project meter as of this writing?
Where can I find the schema and BOM?
Great project idea, BTW!
MCU clock is 8 or 16 MHz, optionally 20 MHz with m-firmware. Documentatiion is avaliable at https://github.com/svn2github/transistortester/blob/master/Doku/trunk/pdftex/english/ttester.pdf for example. There's also a directory with PCBs for the tester and hardware options.
Last week I assembled my first transistor tester (bought the kit on Amazon). It appears to be working but there are a few strange things going on. Maybe you can help me in troubleshooting it? It's the kit in a red PCB board with
k1036038s
2578AY-AT
It's the same layout as shown in the attached picture (taken from the net, probably this very forum).
It came with firmware version 1.12k and a spare 7550 (for which I was unable to find a datasheet) and I have already done the calibration procedure twice - from the menu.
Here are the oddities, in no particular order:
0 - After hours of non use, battery voltage is reported lower than what it actually is: at startup it says "Battery 8.9V while the actual battery with no load is 9.2 V (IIRC). This could be just a loading effect, but it is worth mentioning it. See also point 4
1 - When I repeat the measure of a resistance I get increasingly lower values. A 12.5k resistor is given as 12100 ohm the first time, 11980 ohm the second time, 11648, 11245, 10956, 10437, ... (I am making up the values right now, but that's the trend - with the resistor untouched and only subsequent pressing of the knob I went down under 9k with no fixed point in sight). And this is bad.
2 - The same is going on for caps, but I could attribute that to the fact the the measuring procedure is charging them a bit 9316 pF, 9281pF, 8953pF, 8619pF, 8307pF,... and these are actual values just measured with the time between them due to typing the numbers in this post.
3 - The spare 7550 is not identified. Is this normal for this firmware version?
4 - I just noticed that battery value too is getting lower at each pushing of the knob, only to come back to 8.9V if I leave it off for a long time.
What do you think?
there mus be a cap somewhere that is not discharging?
It came with firmware version 1.12k and a spare 7550 (for which I was unable to find a datasheet).
4 - I just noticed that battery value too is getting lower at each pushing of the knob, only to come back to 8.9V if I leave it off for a long time.
What do you think?
there mus be a cap somewhere that is not discharging?
Last week I assembled my first transistor tester (bought the kit on Amazon). It appears to be working but there are a few strange things going on. Maybe you can help me in troubleshooting it? It's the kit in a red PCB board with
k1036038s
2578AY-AT
0 - After hours of non use, battery voltage is reported lower than what it actually is: at startup it says "Battery 8.9V while the actual battery with no load is 9.2 V (IIRC). This could be just a loading effect, but it is worth mentioning it. See also point 4
...
4 - I just noticed that battery value too is getting lower at each pushing of the knob, only to come back to 8.9V if I leave it off for a long time.
[...]
What do you think?
there mus be a cap somewhere that is not discharging?
@hapless, you didn't answer my question. Just because the 2.5v reference is present it should NOT be the default reference. If the 2.5V reference is a crappy TL431 and the Vcc regulator is much more accurate then I may want to use the Vcc as a reference and not the 2.5V. On the other hand, if I have a very precise 2.5v 0.1% reference (not a TL431) and the Vcc regulator is a crappy 7805 5% then I may want to use the 2.5V as a reference.
Again, the question is what determines whether the tester is using the Vcc (5V) as reference or the external 2.5V reference and how do I select which one I want to use?