Alarm Beam Detector when powered with 12v 2A DOES NOT WORK

[nichos]

Hi,

I purchased this ALARM BEAM DETECTOR below from eBay but does not work
when 12v powers both Tra.& Rec.

I powered another make (Zin Zan) 8 years ago & still works OK today.

In the attached image 5 I connected a 12v 2A adaptor & a piezo buzzer but it does not work. The buzzer when powered separately works OK.

Image 9 shows my test rig for Transmitter & Receiver.

Can anybody point out what connections I should make in image 8 to make the buzzer work when the beam is interrupted?.

http://www.ebay.co.uk/itm/Alarm-Dual-Beam-Photoelectric-Infrared-Detector-100M-Home-Garden-Security-LN-/161915006278

 

[BradtheRad]

Ebay has become a haven for vendors from the far East. Merchandise is not always top quality.

The obvious question is, does supply V drop when it supplies both units?

Or another question, does it lead to excessive ripple? If the supply has too much ripple, then it may result in unstable operation. You'll need an oscilloscope to verify whether the supply is stable DC.

 

[nichos]

I used my own mains adaptors a separate one for each, as T & R will be about 20-30ft apart & in fact the T's is 12v 2A & the R's 12v 3.3A.

Forgive my ignorance but, does this sort of Amperage would be adequate?

I have no idea what the ripple bit means.

The other Chinese beam I installed yrs ago has one adaptor for both, & the power cable was the only connection needed.

 

[BradtheRad]

It's a question whether having too much equipment on the power supply, disrupts the smoothness of its output. Or its volt level.

Power supplies typically have a smoothing capacitor at the output stage. It is supposed to reduce the up and down fluctuations (known as ripple). It needs to be a large enough value to do the job. If it is not then you may get abnormal behavior from your equipment.

My reply is simply speculation about the most obvious possibility. As a test, you can try other power supplies, to see if you get better performance. Etc.

 

[nichos]

Can you at least advise on the connections to the 3rd image to try if I can get it to work? .....thanx .....nick