Printed circuit board tester??!!

[arieliwish]

Hi all,

Hopefully some of you wonderfully knowledgable disers out there will be able to help me! My DS (9) has been to maplin and bought a couple of small electrical circuit board kits and soldering iron scared1: DH fault!), and has blundered his way to build them, however some LED lights on the kits work and others don't, so therefore I assume we have a broken connection somewhere.

SO - is there any kind of circuit tester we can buy to find out where the break is, or which component is faulty??? (I seem to remember from my YTS ITEC course that LED's were notoriously dodgy!)

I've been back to maplin tonight and asked one of the staff but he didn't have a clue, and after looking in the catalogue for 10 mins advised me to look online to see what we need!!

Fingers crossed!

Lynn

 

[Dimplenose]

DH says the LEDs might be the wrong way round - they only allow electricity to pass in one direction. He says a multimeter will tell you if there is current either side of the LED - but isn't knowledgable enough to recommend a particular multimeter.

 

[Tron[ADS]]

LED's can be quite easy to blow if they are fitted in reverse polarity.
Easiest way to test one is to hold the 2 terminals onto the solder points (or legs) of one of the ones you can see is definitely working....they should both light up, if not, the suspect one will remain off.

With regards to testing the circuit, its difficult to advise without it in front of me, but a starting point would be to use any multimeter set to DC Volts (Range up to about 12V should do it), hold the black terminal onto the battery (or power supply) -ve , and probe the red terminal to the +ve point of all the LED's in question...where you get no reading you know that somethings gone wrong around that area, and in conjunction with the circuit diagram you should be able to trace back.

 

[Goofyish]

For basic testing any digital multimeter should be OK.

Something like this:

http://www.screwfix.com/prods/14469...ircuit-Testers/Autoranging-Digital-Multimeter

If you want a really good quality meter then look for a Fluke - although you will be looking at about £170+ including calibration certificate!

As others have said above, an LED is a diode, so only allows current flow in one direction. So you need to ensure they are the correct way round.

To tell which side of the LED is positive (anode) it usually has a longer lead. There is also usually a 'flat' on the negative (cathode) side of the LED body.

 

[arieliwish]

Hi guys,

Thanks for your replies, we're going to look for a multimeter over the next few days, prob at the cheaper end of the scale though.

The LED's are def in the correct way as the boards in the kits come with outlines of the components printed on, and the LED outlines show where the 'flat' side goes. I have a feeling its more to do with DD and DS soldering skills, prob blew one of the components up! We have had success with a small 'torch' kit and are half way thru a 'spy bug' kit, so will keep you posted!

We'll prob chalk the first two failed kits up to experience if we can't get them to work!

So much for this being DS pocket money hobby!!

Oh and FYI if you're ever using a gas soldering iron, have your solder hand high up coz it doesn't half get a hot blast from the flame hole!!! OUCH!

Lynn