Neither fan or thermostat respond when 12 v. applied at connector. 12v supply tested—steady 11.8volts. Fan on its own works OK on 12 v. When fan and thermostat leads combined, fan oscillates but does not revolve. With 12 v connected, meter reading from socket records variable voltage from 20 to 8 volts. Component view shows two flying leads at R5 and R7 to facilitate experimentation re hysteresis and temperature. There is a short circuit somewhere but I cannot find it. I have taken the precaution of sending links to photobucket with top and bottom views of the circuit in the hope that you might be able to advise me as to what has gone wrong. Thank you.
A couple of thoughts:
Sorry, there is only one pic showing the component side. There is no solder side pic. It is rather unsharp.
Is the IC mounted the correct way round? Judging from the picture, we think it is inverted.
Extending resistors with leads is not a good idea and can lead to oscillation.
How did you connect the unit to the fan?
What power supply do you use?
There is no sensor connected, did you connect the sensor?
Thank you for your quick reply. The power supply is 12 volt rated at .5 amp. The 12 volt fan draws .07Amp. Originally, the power and fan leads were combined and inserted in 12v. supply socket. Re-orientation of the IC has solved the power supply problem. The fan operates and I assume 12 volts is getting to the thermostat circuit although the mains powered 40W. bulb does not light up. A meter across the screws of the 12v. supply socket shows a steady 11.8 volts I did send a link to the solder side but I do not know what happened to it and I have done another which I hope is more successful. I did have the sensor wired in when testing .
img]http://s581.photobucket.com/albums/ss256/cafecremephoto/?action=view¤t=08112011043.jpg[/img
An IC that has been inserted the wrong way round is most likely defective.
What happens when you power the kit and when you turn the pot?
Can you hear the relay click? Does the led light?
Sorry to say, but the soldering looks poor and might need re-work.
Thank you for your reply. When 12v power is applied, LED does not light , the relay does not click and variation of pot. setting makes no difference. The fan does operate when power is applied. I will get a new IC and rework the soldering. Hopefully, I will get back to you with better news.
Velleman 417. I have inserted a new IC LM324N as suggested. Doubtful soldering has been reworked . 12 V and 230 V supplies re-connected . Fan operates but LED does nor illuminate and heater does not light. Variation of pot. setting makes no difference. I am at a loss as to what I should do now and would value your further advice. Thank you.
I’m sorry, but it looks like we do not seem to be able to help you trough this forum.
One final option we can propose is to take a look at your kit and perform testing/repair.
You can mail your kit to:
Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium.
Thank you for your efforts. Bearing in mind costs of postage etc. it looks as if fourth new kit beckons.