I have a problem with my temperature sensor with LED display.
When i was finished soldering the whole kit, i dubbelchecked is everything was in correct position ect. ect. ect. And everything was right. But when i switched on power, nothing ever happened. I’ve even disconected the sensor just to see if i would get the ERR sign that it should have gave me but it didn’t. Now, I triplechecked if there weren’t any short-circuits. Since there was none, i started meauring and i immediately found that there was no current over ZD2. Since i’m an student electronics, it didn’t take long to find out that ZD2 should bring the current down for IC3. the problem is, in stead of having 5.1V over ZD2, i only have 0.71, so it works like an normal diode. I’ve replaced the ZD2 Zener Diode with an exact the same one but still no luck… Now me and my teacher think the diode is put on backwards. But it sits in the correct order with the line on the diode on the line on the print.
I surely hope you can help me.
Ask me anything you want, i’ll give you anything you want (info ofcourse :lol: )
Since it’s an integrated test ( we have to order, build and provide info of the thing we’ve build for a jury) to see if we’re qualified electronics, I would really want to see this temperaturesensor work.
This is a strange problem. If you have replaced the zener and you still measure 0.7V, altough it is put in the right way, then I must assume that IC3 is pulling the supply down to 0.7V.
Remove it from it socket en measure over ZD2. If you now have 5V1, then we must conclude that it is defective. If it is defective, return it for examination and/or exchange. If you still measure 0.7V, then you must check for an assembly problem.
ok, i got it to work but now only DY1 lights up. He reacts fine on the sensor but it’s the only one working, even when i short-circuit the senso, it says R, whilest DY1, DY2 and DY3 should give ERR. Thanx so far, I asume there was a bad contact on the IC3 pens, since they are matt-grey in stead of shiney…
As one display works, the 7 segment lines are probably OK.
Check the multiplex line of the display circuit.
We suspect another assembly problem, as you already encountered one.
well, now now display works.
Also ZD1 becomes Verry hot, and there’s no voltage between IC3 connectors 1,2,17 and 18 and resistors R16, R15, R14 and R13. If you look at the manual you’ll know what i mean. IC3 recieves his voltage, but there isn’t any leaving the IC. Please help me, as i only can work on tuesday morning on this project…
This is a strange problem.
Make sure you did not confuse T4/T8, T3/T7 etc…
It is very likely that an assembly problem is causing this behaviour, however, we do not have the means to solve this problem by mail.
If you cannot get it to work, please return your unit for examination.