How to make a GAM Check

JP12687

Active Member
Joined
Aug 23, 2004
Location
Stamford, CT
I wish to make a GAM check...just the part that checks the lamps..i am using twistlock connectors and have extra laying aroud that i can use in the connection..i just need to know what else i need.
 

Mayhem

Senior Team Emeritus
Premium Member
Joined
Jan 21, 2004
Location
Australia
Let me get this straight - you intend to plug this into a fixture to check the lamp. The fixture is unplugged, NOT LIVE.

I know - sounds pretty simple but I want to be very clear about this as I have no idea how much you (or other people reading this post) know.

If this is what you will be doing, place the following between the Hot and Neutral pins:

Hot - 9V Battery - 370 Ohm resistor - LED - Neutral

What happens now is that when you plug the fixture into this tester, the lamp will complete the circuit by connecting the hot and neurtal, thus illuminating the LED. If the LED doesn't light up, check your lamp (don't simply throw it away as there could also be a fault elsewhere in the fixture).

You could also place a LED between the resistor and Ground to test for shorts. This LED would only light up if there was a fault (I would use a RED LED).

NOTE: that this will only check lamps that are not controlled by any internal circuitry, such as inteligent lighting, strobes etc. It can be used on Par cans, Fresnels etc.
 

JP12687

Active Member
Joined
Aug 23, 2004
Location
Stamford, CT
how do i hook it all up. like how do i hook up the 9v bat 50 ohmresistor and the LED?
 

Mayhem

Senior Team Emeritus
Premium Member
Joined
Jan 21, 2004
Location
Australia
Are you referring to the actual connections or in what order the components are connected together?

I would solder the connections and use a battery clip on flying leads.

Now - in Australia, we make these using small plastic boxes with a surface mount receptacle and the LED(s) mounted into the box. The battery, wires and resistor are inside. Use either a battery clip or some double-sided tape to keep the battery from moving.

Now - in the US - you guys have more plug and receptacle types and I really have no idea as to the size, shape and configuration of them all. Looking at the GAM check on the web (and having no size reference to work from) I would imagine that you could fit it all the components into the actual receptacle. You would have to use a smaller battery and I would imagine that a 3V lithium would do the trick. If so, get one with leads or tags already on it as it is much easier to solder to them than to the battery directly.

Essentially you connect one side of the battery to the Hot connector in the receptacle. For this lets say you connected the positive side of the battery to hot. You then connect the negative side to one leg of the resistor and the other leg of the resistor to the Anode of the LED (the anode is the longer of the two legs). The Cathode (shorter of the two legs) then connects to the Neutral connector of the receptacle.

Note: The value of the resistor varies depending on the size of the battery that you use:

1.5V use no resistor
3V use a 70 ohm resistor
6V use a 220 ohm resistor
9V use a 370 ohm resistor

These calculations are based upon a 20mA LED and uses the formulae:

R=(E-1.7) x 1000/I where:

R= resistance
E= voltage
I= the LED current in milliamps

So for a 9V battery R= (9 – 1.7) x 1000 / 20 = 365 (round up to 370) I made a mistake on my initial post when quoting the resistance, which I have now fixed.

Also, if you are unsure as to the anode (+) and cathode (-) legs on the LED, have a look at the actual plastic ‘light’ part. The flange that runs around the bottom of this will have a flat side. The flat side corresponds with the cathode.

To test it, use a piece of wire to short the Hot and Neutral connectors.

I think that whatever receptacle you use, you will have to make up adaptors if you want to use more than one type of plug.

Now – if you wanted to add the Hot to Ground short test, all you have to do is add an additional LED. To do this you would solder the anode of the second LED to the resistor, at the same point to which the first LED connects. The cathode of the second LED then connects to the Ground pin on the receptacle.

PM or email me if you have any problems.