Have we any electronics guys on here?

johngalway

Hi folks,

I just went looking at Debens electronic dimmer switch, since one of mine died recently. Bloody hell, £42.95 like. It's a bit much.

When I finally decided mine was dead I opened it up for a look. There isn't a huge amount inside, though I suspect everything adds up cost wise as in everything.

Are they worth the money for what's in them? I've used them and find them handy, still, it's a lot to shell out.

Who would be supplying Debens or are they made in house I wonder?

Has anyone outside Debens and Opticswarehouse tried making them - properly now, not bodged DIY.

Just thinking out loud.... Ohhhh Ecccchhooooooo....

rowa

the dimmer would just be a variable resistor as far as i know , does the broken one have any numbers/specs on it ? you should be able to get one from radionics or maplin mail order .

FarmerGreen

Its more likely to be a pulse width modulated (PWM) switcher.
Let me google that for you :-
http://www.ctshooter.com/dimmer.html

spideog7

Can't imagine it's that hard, I made up a rig for mine that allows me to use different brightness setting, but mine uses super bright LED's so it was a fairly complicated circuit, all you really need is a couple of resistors.

What do you need, is it a linear dimmer or just a couple of different brightness settings?

Yea the problem with this is that you're using fairly high current so just putting a resistor there (although it'll work) is going to cause it to heat up alot and therefore waste your available power. A PWM is much more efficient but I still don't see it being too difficult to build, if you're anyways handy with a soldering iron.

EDIT: Just saw FarmerGreen's reply, that's exactly the cct. I had in my head, I must have learned something in my degree All you have to worry about there is making sure the MOSFET is rated for the current you're putting through it, and then whack a massive heatsink onto it, the rest of the circuit doesn't have to deal with the high current at all.

FarmerGreen

Just looking at some mosfet specs Rds is only 0.2 ohm for the STP55N06
So even at 5 amps its only dissipating 1W
http://www.rapidonline.com/sku/Electronic-Components/Discrete-Semiconductors/MOSFETs/TO-220-Power-MOSFETs/66264/47-0530

clivej

John I had the dimmer from Opticswarehouse running my Lightforce 170 100watt lamp last night for 1/2 hour and it didn't get hot or go phut/bang.

I know it's rated @5amps max but @£;29+post it's seems good.

I remember someone else using the Opticswarehouse dimmer from here, maybe search for the post and PM him to find out if his was OK.

or not:p

demonloop

John,

You have PM

clivej

rowa wrote: »

the dimmer would just be a variable resistor as far as i know , does the broken one have any numbers/specs on it ? you should be able to get one from radionics or maplin mail order .

A variable resistor will work but it's not the best way to go as it will still take the same current and can hot.

The dimmer works by a high speed switching circuit.

spideog7

555, MOSFET, resistors, capacitors, diodes, variable resistor, bit of strip board.
Thermal paste, heatsink (or metal box), electrically insulating washer.
Switch.

The most expensive things on that list are the thermal paste and the box to put it in, other than that I'd say you'd do it for E10.

clivej

spideog7 wrote: »

555, MOSFET, resistors, capacitors, diodes, variable resistor, bit of strip board.
Thermal paste, heatsink (or metal box), electrically insulating washer.
Switch.

The most expensive things on that list are the thermal paste and the box to put it in, other than that I'd say you'd do it for E10.

And do we just throw them all in the box and conect up the lamp to it?????????

Or does it involve a soldering iron and some gray matter to sort it all out?????? :rolleyes:

Here's one I made. Don't know what it does

ormondprop

would a volume control unit for speakers be the same princible? and if so could you rewire one to work with a lamp

clivej

ormondprop wrote: »

would a volume control unit for speakers be the same princible? and if so could you rewire one to work with a lamp

Yes but not in the sense that you mean. Just on it's own in series with the lamp then NO.
But when used with a voltage/current regulator to control the regulated output then yes.

This is getting all to complicated. Just buy a dimmer to do the job and be finished with it.

Opticswarehouse dimmer @£;29.95 and get a Coiled Extension Cable 2m at the same time @£;7.95

spideog7

clivej wrote: »

And do we just throw them all in the box and conect up the lamp to it?????????

Or does it involve a soldering iron and some gray matter to sort it all out?????? :rolleyes:

Here's one I made. Don't know what it does

Well from his other post over on the hunting forum I know that johngalway has a soldering iron and solder and from reading his posts on here he isn't lacking in grey matter, plus he's a Galway man so I have plenty faith in him


Oh and I can explain that to you if you're interested

EDIT: I just looked at that circuit it looks like some sort of transmitter definitely not a PWM anyway :P

Glensman

clivej wrote: »

Opticswarehouse dimmer @£;29.95 and get a Coiled Extension Cable 2m at the same time @£;7.95

John doesnt like the coiled leads. They make way too much noise and get caught on everything.

I bought a deben dimmer for about 35 sterling. The feckin thing doesnt work. at all.

Vegeta

spideog7 wrote: »

555, MOSFET, resistors, capacitors, diodes, variable resistor, bit of strip board.
Thermal paste, heatsink (or metal box), electrically insulating washer.
Switch.

The most expensive things on that list are the thermal paste and the box to put it in, other than that I'd say you'd do it for E10.

Wouldn't be a bad project for the forum. The Boards.ie PWM dimmers

FarmerGreen

What are the ratings are the of the bulb, volts? amps? or watts.

clivej

FarmerGreen wrote: »

What are the ratings are the of the bulb, volts? amps? or watts.

12 volts, <9amps, 100 watts.

meathstevie

What about the car clocks cluster dimmer switches ? Would they be any good. You can get those for next to nothing in breakers yards.