I bought and assembled the digital tachometer kit. When I apply +12VDC from my power supply to the plus and minus inputs, the meter shows “00”, as it is supposed to do.
However, when I connect 12VAC to the - and IN inputs, the meter still shows “00”. I’ve checked my soldering numerous times. What should I check next?
[quote=“juice”]I bought and assembled the digital tachometer kit. When I apply +12VDC from my power supply to the plus and minus inputs, the meter shows “00”, as it is supposed to do.
However, when I connect +12VAC to the - and IN inputs, the meter still shows “00”. I’ve checked my soldering numerous times. What should I check next?[/quote]
You should attach a positive supply to a negative or ground?
You should use 12VDC not 12VAC?
Hi and thanks for your quick response 
50Hz signal should be used for calibration and it ought to be attached to minus and in, so I think it must be alternating current. Of course I have the DC supply connected to plus and minus at the same time.
Am I doing something terribly wrong while trying to calibrate?
EDIT: Live is attached to in and ground/neutral to the minus.
Make sure ZD1 is correctly mounted.
The polarity of ZD1 is correct and soldering work is fine. Seems to be a working zener as my meter shows around 770 ohms.
Oh, and just in case, D1 and D2 give a value of 670 ohms, so I’m quite sure that I haven’t mixed a zener with a 1n4148. And it looks different, too.
Does anybody have an idea?
Well well well, I sent it to repair and got it back, IC3 was broken.
But when I try to calibrate it for my 1-cyl. four-stroke engine with 12VAC 50Hz, I get values from 8 to 25 (x100 RPM), so not even near 60 no matter how much I turn the potentiometer. What’s wrong this time?
Try increasing RV2 to 250Kohm
Thank you, seemed to do the trick. At last it’s working. Why isn’t the increasing of the resistance mentioned in the manual?
It is very rare that it needs to be changed. It will be included in the next version of the manual.
Hello,
I thought it would be best to ad my question to this topic because it is about the same kit.
While I was building my kit I came upon the step I needed to install the trimmers (RV1 and RV2) Wich should be RV1=100kohm And RV2=47kohm.
When I took the trimmers out of the package I noticed that the only thing that was marked on the trimmers was 50k326m and 10k404m. and there is a third one included asswell with 100 k so that should be rv1 not?
So My question is which one is RV1 and RV2
Regards
47K = 50K
Use of 10K trimmer is explained on page 6 of manual.
[quote=“brokenbmx”]Hello,
I thought it would be best to ad my question to this topic because it is about the same kit.
While I was building my kit I came upon the step I needed to install the trimmers (RV1 and RV2) Wich should be RV1=100kohm And RV2=47kohm.
When I took the trimmers out of the package I noticed that the only thing that was marked on the trimmers was 50k326m and 10k404m. and there is a third one included asswell with 100 k so that should be rv1 not?
So My question is which one is RV1 and RV2
Regards[/quote]
I also used a 100k RV1 and a 50k RV2, but today I switched to a 100k RV2 because I also couldn’t reach 30 at calibrating for a 1 cilinder 2-stroke. After that I could easily set it to 30, but when I connected it to my 200cc vespa, it displays a nice 13-14 when idle, but when it revvs up, the display goes to 00… Then I put a 10k trimmer parallel to the zener as described in the manual, but then the display keeps displaying 00 (when idle and on higher RPM) and it doesn’t matter how I set the trimmer (=potmeter in NL?)
I could appreciate if someone has a solution!!
And does anybody know the ‘refresh rate’ of this thing? If it’s too ‘slow’ I better put on an analog one…
Doesn’t anybody have an idea on my previous post?