Hi, desparate for a little help here!

[DaveC]

Hi everyone,

Can anyone give me a little advise on this little problem i have; my brain has stopped working and can't think anymore!!! :lol:

From a variable voltage of 0 - 10vdc i need to be able to control a variable resistor, in other words, at 0vdc i need a resitance of close to 0ohm and at 10vdc i need to see a resistance of around 10Kohm. the scale would be preferably linier.

This is to control an electronic dimming circuit. The problem is, my controller card outputs 0 - 10vdc (0 volts being 0% and 10volts being 100% brightness) but my dimmer module is designed to be controlled with a vairiable resistor across an internally generated 0 -10vdc supply to control output brightness. So, if i can use some kind of electronic variable resistor if you like, the dimmer module would just see it as a standard variable resistor across it!

I hope i have given you enough information here to be able to help me, and look forward to a reply soon!


Thanks very much

Dave

 

[Oznog]

Variable resistors are quite odd to create. Very unusual.

Generally, it will be far easier to make a new dimmer circuit that can be controlled the way you want to.

Or look into just how the dimmer reads the voltage on the resistor so you can give it a voltage. But it might be simpler to build a new one.

 

[olly_k]

I assume the dimmer has some two pin socket that has 10v output and sampleing input right?
Assuming the dimmer electronics are isolated from the mains supply....

See if this 10v internal supply (for VR) of the dimmer is 10v in respect to the common ground of the dimmer. If so wire the dimmer ground to your variable supply ground and and the external 0-10v to the sampling input.

BE VERY CAREFULL - THE DIMMER ELECTRONICS MAY NOT BE MAINS ISOLATED AND COULD RESULT IN ELECTRIC SHOCK AND / OR SERIOUS DAMAGE TO EQUIPMENT!!!!!

If so you will need to keep both modules 'isolated'. You could use a voltage to frequency convertor using a 555, interfaced to the dimmer via an LED and LDR / photo transistor combination. The variable pulsing of this circuit could be made to emulate the properties of the VR. I think you would almost certainly have to smooth the pulsed output to a steady DC voltage, maybe use a freq. to voltage convertor on the other side for best result. - A pulsed voltage at the input could cause serious confusion to the dimmer electronics :wink:
Just some ideas...

 

[DaveC]

Hmmmm, some interesting ideas..... i was kind of thinking about the 555 timer as an oscillator... may have a play with that one!!!

any more ideas?

The product sheet i can see is fairly useless to be honest but it is here if anyone is interested!

**broken link removed**

Around page 33, 34, 35 is the product and some more charactoristics, the bit i'm actually doing is the 'Analouge Output' section.

I'm well conversed with dimming systems as a lighting engineer, but this one has me stumped!

Thanks alot for your help so far, this sites dead usefull!


Dave

 

[Nigel Goodwin]

0-10V was the old standard lighting control format, back before DMX took over - have a look here for a design using this format **broken link removed**. You should be able to utilise just the parts of the design you want.