Motion Sensor Device

What happens with the relay voltage when you disconnect the basis of the transistor? Depending on how it is soldered, you just might be able to cut the leg (with the voltage off) Normally the voltage over the relay should disappear - if not place that transistor under suspicion for deportation or vertical filing into the trash. If nothing changes, you can always solder the cut base ends together. Anyway you have checked the transistor in a semi destructive way. Then proceed to the IC. I just make a guess that the IC feeds the transistor, that activates the relay. Try to give some more details.

Hy dymdsc,

Thank you, it was the transistor. I repaced it and it works.

I learned again to look first at the simple things.

You may have had a short dropout in voltage causing it to go into default on. Try turning off the power for one minute. Then turn it back on and see if it clears up. Some sensors can be over ridden by turning them off and back on right away so they stay on constantly.

Yes that happens to an other similar sensor I have installed.

Hi Joachim, Just to re-iterate Charsley 99's comment - most of these units will default to On if you momentarily interupt the supply. - they usually need a 10 to 20 second interupt to re-set to normal operation. Also, some are equipped with potentiometers to set sensitivity and dwell time. The location of these is not always obvious Good Luck!

By the way, I had to junk one of these which refused to turn on in sub-zero temperatures - but, given your location, I guess that's NOT part of the problem!

Hi Zadok, you are right, I think exactly the opposite happens to an other sensor i've installed. It turns on because it is to warm.

For IC spec sheets please go to www.alldatasheet.com and this will help you understand the discrete and ICs of your device.