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lighted switch help

hi

not really familiar with this stuff, thought it would be simple but i got stuck

I have a preamp (low power) it gets 12v and i have a power supply also 12v(DC)

i bought a lighted toggle/rocker switch lighted from radio shack

my goal was to just have the switch turn on/off the amp and light in the on position

the switch has 3 legs labled

gnd

load

power

sounds simple, but seems something is not quite right

I assumed gnd was ok to tie everything to

so i have gnd from preamp gnd from pwr supply and i connected to gnd on the switch

i assumed load was supposed to goto the pos on preamp

and power whent to pos of the supply

blew fuse i think power also switches to gnd or something i dunno

anyone have experience with this type of switch from RS and how to hook it up?

thanks

Reply to
ml
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ML-

What is the Radio Shack part number? I would have assumed the same as you. I wonder if the switch might have been assembled with the labels backwards?

With the switch in the OFF position there should be an open circuit between Power and Gnd, and lamp resistance between Load and Gnd. With the switch in the ON position, Load and Power should be shorted, and lamp resistance between either and Gnd.

That is assuming the lamp is intended for 12 Volts. If it was intended for 120 Volts, it most likely would be a neon lamp in series with a resistor, and would measure as an open circuit.

Fred

Reply to
Fred McKenzie

hi

thanks for responding it's 12v dunno if it's led or lamp

part number

formatting link

Model: 275-712 Catalog #: 275-712

Reply to
ml

What is the rated power output of the power supply? If it's a small one only feeding a pre-amp it likely can't drive the 5 watt or so lamp in the switch. Which could take over 500mA at switch on. A better choice would be an LED - only about 20mA or so.

Generally car stuff like this isn't too concerned about efficiency.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

Connect to the -12 Volt output of your power supply, and the -12 Volt lead of the preamp. it is also one side of the lamp.

This is the switched power for the lamp, and to the + 12Volt input on your preamp.

This goes to your +12 Volts.

Did you look at the link? There is no way the lamp is 5 watts. It would melt the switch's body. It should be 10 to 50 mA. Think 'Grain of Wheat' lamp.

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Reply to
Michael A. Terrell

Whatever. But the principle remains - filament lamps have a high start up current which could be too great for a small regulated supply.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Dave Plowman (News)

Where did he say the supply was that small? If it won't handle the preamp & the lamp at the same time its too damn small, anyway. Even small wall warts start around 200 mA.

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Reply to
Michael A. Terrell

He didn't.

FFS. Try measuring a small filament lamp start up current. Illuminated car lamps switches could easily be too much for one - they might have to be visible in the daylight.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Dave Plowman (News)

I did. About 40 years ago. They were in the 10 to 50 mA range.

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Reply to
Michael A. Terrell

So you know for sure what size lamp that switch uses? I couldn't see any information on the website.

However, 50mA might well be too much for a marginal power supply - as I said

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

Hi folks

appreciate the head up regarding power to the lamp, my supply would have enough power to light a small lamp

what i didn't get is a way to wire it up , which was my question

one person responded back with exactly the same why i listed it hooked up which didn't make sence to me since i listed it as that didn't work

clearly something is off on these switches googling around others agree but no one listed (on the other sites) how to actually hook it up

it's gotta be something simple

something is not right

Reply to
ml

The way you wired it was correct.

Could it simply be faulty? The easy way to check it is with a DVM - they can be bought for pennies these days.

I'd agree there.

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    Dave Plowman        dave@davenoise.co.uk           London SW
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Reply to
Dave Plowman (News)

If it is that marginal it would be useless for the preamp, as well.

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Reply to
Michael A. Terrell

Trimmed

I would think from the labels that you had hooked it up right. A simple test would be to use an ohmmeter and check that the connection between power and load actually switches when the rocker is moved from position to position. If it does once again you should check the resistance from the gnd terminal to each other terminal with the switch actually off and see if there is a possibility the led or bulb is actually shorted.

Generally a led will read as an open circuit unless your meter supplies at least 3v to the test leads while a lamp will read a low resistance.

A possibility also exists that your supply is putting out a high level of ripple and could be causing the led to act as a short. This possibility can be checked by hooking up your multimeter and monitoring the amount of AC present. Small wall warts usually contain little or no filtering and depend on the equipment its meant to power for final filtering and some are pure AC.

If this is the problem a diode with the cathode connected to power ground and the anode connected to the witch ground terminal might solve the problem.

Since the switch is intended for automotive use it is also possible that the indicator is a high current lamp and overloading your supply.

Gnack

Reply to
Gnack Nol

thanks for the reply, i can light the bulb or led so it's bad my supply is fine, no ripple and it has enough amps for the job good theory thou

i'll have to see apprantely the diagram on the switch could be wrong i dunno

but the fact that others have the smae problem at lest means i am not crazy

guess i need to really figure it out somehow

again thanks very much

Reply to
ml

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