# Vol. 6, Chapter 7, Experiment #6 heat problem.

#### NCGrimbo

Joined Aug 19, 2005
4
Hi all. I wanted to add an on/off switch to the LED Sequencer experiment. I got a lighted, 12V rocker switch from Radio Shack and connected the ground plug to the ground on the battery, the middle power plug to the positive on the battery, and the remaining plug went to power input for the circuit. IE: The switch sits between the battery and the 1M Ohm resistor on the picture.

I have alegator clips on the battery terminals and when I run the circuit with the new switch, the clip on the negative terminal of the battery gets hot. I assume that this is not a good thing. Any hints on what is happening?

I'm a newbie to circuit designs and have a great understanding of the logic, but not when resistors and capacitors are needed.

Thanks

#### mozikluv

Joined Jan 22, 2004
1,435
Originally posted by NCGrimbo@Aug 24 2005, 02:34 PM
Hi all. I wanted to add an on/off switch to the LED Sequencer experiment. I got a lighted, 12V rocker switch from Radio Shack and connected the ground plug to the ground on the battery, the middle power plug to the positive on the battery, and the remaining plug went to power input for the circuit. IE: The switch sits between the battery and the 1M Ohm resistor on the picture.

I have alegator clips on the battery terminals and when I run the circuit with the new switch, the clip on the negative terminal of the battery gets hot. I assume that this is not a good thing. Any hints on what is happening?

I'm a newbie to circuit designs and have a great understanding of the logic, but not when resistors and capacitors are needed.

Thanks
[post=9898]Quoted post[/post]​
hi,

what you have done was to have a short circuit. you have a single pole single throw switch with 3 terminals. you have the upper and lower terminal and the center terminal. you can connect the positive line leading to your device on the center terminal. then connect to any of the upper or lower terminal your battery positive line. then connect directly the device negative line to the battery negative terminal.

moz

#### NCGrimbo

Joined Aug 19, 2005
4
OK. If I read you response correctly, I don't connect the negative of the battery to the switch. I'll give that a try tonight.

Thanks

#### NCGrimbo

Joined Aug 19, 2005
4
I hooked up the switch as you suggested and it works, but now the light on the switch does not light up. I assume the light needs to be connected to the negative pole of the battery, but that puts me back in the situation where the clip overheats.

Any other suggetions?

#### nomurphy

Joined Aug 8, 2005
567
You need more data on the switch, it may be a LED or a bulb, and you need to know the configuration. Did it come with a paper description, or on the back of the package?

If there are only three terminals, then one side of the LED/bulb is referenced to one of the other terminals (and both when the switch is closed). This means that the light terminal must go to either ground or Vcc, depending it's orientation.

Use a DMM and find which two terminals close and open with the switch. Let's assume it's the top and bottom; connect the top and bottom of the switch between the battery (+12V) and your project (Vcc). Connect the middle terminal (LED) to ground. This assumes there is a built-in ballast resistor for the LED. If not, connect a 1K between the center terminal and ground, none would be needed for a bulb.

(I suspect it is a 12V bulb).