Dimmer Switch

Ian P. · Posted: Sun Aug 01, 2004 4:25 pm Post Subject: Dimmer Switch

Hi,

I'm trying to set up a simple one-way dimmer switch to control the speed of a windscreen wiper motor from a 12v car battery. I'm using a 2 core cable (live and neutral) and just cant seem to get it wired properly!

I've cut the cable and fed both of the live wires to the live port and both of the neutral to the neutral (as it shows on the instructions) but I just cant get it to slow down. Any ideas??

Thanks
Ian

kendor · Posted: Sun Aug 01, 2004 4:29 pm Post Subject: Re: Dimmer Switch

Ian P. wrote:

Hi,

I'm trying to set up a simple one-way dimmer switch to control the speed of a windscreen wiper motor from a 12v car battery. I'm using a 2 core cable (live and neutral) and just cant seem to get it wired properly!

I've cut the cable and fed both of the live wires to the live port and both of the neutral to the neutral (as it shows on the instructions) but I just cant get it to slow down. Any ideas??

Thanks
Ian

thyristors and DC my dear chap! the thyristor will continue to conduct until you break the supply which is what happens when a dimmer switch is connected to AC (zero crossing threshold point of thyristor/triac device). you will need to look for a different method of speed control, possibly Pulse Width Modulation (PWM). do you have a multimeter with a current measurement facility? if so what is the motor pulling in amps? here's a circuit diagram for a controller see specifications section to work out what output device Q1 FET to use. http://www.solorb.com/elect/solarcirc/pwm1/

Ian P. · Posted: Sun Aug 01, 2004 4:58 pm Post Subject:

Thanks for the reply Kendor,
I dont have a multimeter so couldn't tell you what the motor is doing in amps. I'm bit of a novice when it comes to electrics so PWM is way over my head

!!! I'm trying to keep the cost down as much as possible so what sort of switch would you suggest?

Ian

kendor · Posted: Sun Aug 01, 2004 5:07 pm Post Subject:

Using a switch isn't going to be an option i'm afraid and a variable resistance will just generate loads of heat and is inadvisable in a Car environment the circuit mentioned above wouldn't be too difficult to build if you follow the instructions step by step otherwise you'll have to look for a ready built option which probably won't be as cheap as you wanted.
I'll have a look around and see what's available and get back to you

breezer · Posted: Sun Aug 01, 2004 5:17 pm Post Subject:

what are you doing this "project" for ?

also it MAY be that you cant vary the speed of the motor, dont forget, a windscreen motor is actually connected to a gear box (usually) and it may be that at slow speeds you will not get enough torque to move the blade (assuming that it is still attached?)

you could always try using low value high Watt resistors, but they will get warm to say the least

also to clarify, a dimmer switch is desigen to work on ac, not dc

ac (alternating curent) being the mains, dc (direct current) being a battery

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kendor · Posted: Sun Aug 01, 2004 5:19 pm Post Subject:

One source unfortunately in Australia but they do ship to the UK Bit pricey $45 though
http://shops.bizarsoftware.com.au/ATAShop/catalogue/category16/category37/product84

kendor · Posted: Sun Aug 01, 2004 5:21 pm Post Subject:

breezer wrote:

what are you doing this "project" for ?

also it MAY be that you cant vary the speed of the motor, dont forget, a windscreen motor is actually connected to a gear box (usually) and it may be that at slow speeds you will not get enough torque to move the blade (assuming that it is still attached?)you could always try using low value high Watt resistors, but they will get warm to say the least

also to clarify, a dimmer switch is desigen to work on ac, not dc

ac (alternating curent) being the mains, dc (direct current) being a battery

which is where PWM is the best option as it doesn't stall the motor like a resistance would when the pd across it became too great

breezer · Posted: Sun Aug 01, 2004 5:22 pm Post Subject:

2 things

@45$ customs & excise will want to add their share (i just got a bill the other day from them)

also it is a kit, poster said he doesnt know how to use MM, so probably has no soldering iron either

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kendor · Posted: Sun Aug 01, 2004 5:25 pm Post Subject:

bit cheaper but still overseas
http://electronickits.com/kit/complete/motor/ck1400.htm

kendor · Posted: Sun Aug 01, 2004 5:43 pm Post Subject:

breezer wrote:

2 things

@45$ customs & excise will want to add their share (i just got a bill the other day from them)

also it is a kit, poster said he doesnt know how to use MM, so probably has no soldering iron either

yep kits, having trouble finding ready built.

kendor · Posted: Sun Aug 01, 2004 5:50 pm Post Subject:

well would you credit it, RS seems the best cheapest option (considering shipping costs etc) £33+vat for an easily wired up module just need a 5K pot extra: here

kendor · Posted: Sun Aug 01, 2004 6:52 pm Post Subject:

sorry it appears my link expires after a time so i can give you the order code for the item and suggest you look yourself, if you are able to register ie have or know someone with a delivery point code then you can access the technical info pdf(connection diagram) which i would post if i knew how to upload a pdf file here
RS order code is:330-5364

kendor · Posted: Sun Aug 01, 2004 8:03 pm Post Subject:

here's the manufacturers info on the above component:
United Automation Ltd
1 Southport Business Park
Kew
Southport
PR8 4HQ
Sales 01704 516516
email: Enquiry@united-automation.com
www.united-automation.com
Their product code is:DCM X10335

Ian P. · Posted: Sun Aug 01, 2004 10:15 pm Post Subject:

thanks for the info guys, it looks like its back to the drawing board to see what I can come up with!

Cheers
Ian

breezer · Posted: Mon Aug 02, 2004 4:53 am Post Subject:

but what are you trying to do? (or why are you trying to do it)

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