12V show control how to?

[Dj Dunc]

Hello all.

 

I've moved away from the live events side of things in recent years over to the automotive lighting industry but I'm turning back to my heritage in search of answers!

 

I have a show vehicle we're building at present with a lot of lighting that I want to control via PC software (DMX based or otherwise, currently Vixen and XLights on test). At present I have approximately 300 control channels, of which many will be considered "strings" or "rows"

 

Does anyone know an appropriate method for interfacing between the 12v side and software? Current is max 5A per channel, with the majority at 0.5A or less. I'm running a test bench with the Sainsmart 16 channel relays, linked to an Arduino running as a serial interface, however having 20 of these boards is going to be very audible if the vehicle is stationary. PWM not required at present as I'm not sure how the multi-voltage driver circuits will handle it.

 

I'm sure there will be solutions out there for the theme park industry or installation side of things but I'm stumped at finding anything with a decent channel count! Physically I have a box with approx internal dimensions of 850x350x350 to play with so not too worried about space.

 

many thanks in advance

 

Duncan

[Owain]

use solid-state relays instead of electromechanical ones - will be totally silent.

 

 

[Dj Dunc]

If you can find me a DC SSR that fits the same package then that would work. They do plenty of 16 Channel SSR boards, alas most SSR units are AC only.

 

EDIT: They do now do an 8ch SSR DC-DC board but thats potentially a pain in the derriere as its 40 boards with a much higher cost.

[timsabre]

Use mosfets for the switching, lots of arduino mosfet boards available.

[themadhippy]

multi channel DMX led driver? first hit on google gives a 32 channel DMX unit,all be it rated for 3A a channel max,but 9 of those and an ardunio mega with suitable thyristors hanging of the 50 outputs will do the higher current requirements.

[alistermorton]

Thyristors aren't going to work if its DC though. As Tim said, power MOSFETs is the way to go. If you have DMX you could add power FETs to 30 channel LED dimmers (which you can buy on a well known auction site cheaply) to get the power per channel up and get dimming into the bargain.

 

Edited to fix a typo or two.

[themadhippy]

Thyristors aren't going to work if its DC though.

Do explain why not

[Dj Dunc]

I need to be careful with them that they aren't negative switching (like most LED strips etc) as I have 50 units that are two channel positive switched feeds and common ground.

[DrV]

Thyristors aren't going to work if its DC though.

Do explain why not

Once triggered a thyristor will remain on until the current through it drops to zero. This happens every 10 or 20 mS when running from a mains supply but never happens if the supply is D.C.

It is possible to turn off a thyristor by briefly shorting it out with e.g. a transistor but if you are going to that complexity you might as well just use a transistor on the first place!

[alistermorton]

Thyristors and triacs, once triggered, remain latched on until the current falls below the holding threshold (close to zero IOW). With AC this happens every half cycle. With DC you'd have to intervene to interrupt the current to allow the device to turn off.

 

Transistors only conduct as long as they have bias (or are triggered on, if you like). Remove the bias and they turn off.

 

Thyristors aren't going to work if its DC though.

Do explain why not

Once triggered a thyristor will remain on until the current through it drops to zero. This happens every 10 or 20 mS when running from a mains supply but never happens if the supply is D.C.

It is possible to turn off a thyristor by briefly shorting it out with e.g. a transistor but if you are going to that complexity you might as well just use a transistor on the first place!

 

Beat me to it :-)