# SOLVED (video evidence!) Eurorack power supply question from non-techie

Hello, people that are more knowledgable about electronics than I am.

I have recently acquired a tiny lcd screen which I’m loading into my Eurorack to use with some video synthesis stuff so I can see what I’m doing without looking at the projector. The screen says it is “DC 12v ± 10%” and the power cable ends in a bare black strand (-?) and a bare red strand (+?)

Am I right in thinking that I can power these from a euro power supply so I don’t have to get another wall wart? If so, what’s the best way to do it? Is it just a question of connecting the +12 to the +12 and the -12 to the -12?

Many thanks!

Wait until someone more knowledgable than me answers before doing anything!
But, I am 99% sure one of the wires is for +12v and one for ground. DC 12v is +12v only.
Connecting -12v where it’s expecting ground could fry things

Perhaps it’ll clarify things if I mention that this was intended to be installed in a car

Connect the +12V from your rack PS to the red wire and GND to the black wire.

BUT:

You should look at the power draw of the unit (current) measured in mA. Your power supply will need to have excess capacity greater than the display will draw.

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The screen will need unipolar power. The +12 would go to your +12 and the black would go to GND. (The ± indicates that the thing can take between 10.8 and 13.2V as input voltages - it’s a tolerance).

I’d put money on red being positive and black being GND. But I’d also be remiss if I didn’t say: that’s not a standard, that’s just colours.

Next up: it would be useful as pointed out earlier to find current draw somewhere - it might be in the spec for the screen. A TFT LCD might be quite current-heavy in the land of Eurorack, so your power supply will need capacity to offer it.

A good way to do both of the above would be with a bench PSU: connect it to a 12V unipolar supply and see what the current draw is. A quick scooch on the internet says it might be around the 100-200mA mark, which isn’t huge, but also moderately significant in Euroland.

If all of the above is a go: probably the best thing to do is a small board, stripboard or similar, with 10-pin Euro connector on it, with the +12 and GND connected to either screwterms or soldered to the screen, and then use a standard ribbon to connect it in.

Really, though, those ribbons aren’t designed for powering things outside a rack. I’d probably stick to another wallwart.

Well thank you very much for the information, everyone!

Modular grid told me that I had around 500mA left, so I just tinned the ends of the cable with some solder and stuck them in the right holes… And it works!!! My modular is still alive, I’M STILL ALIVE, and the screen is looking like I spent a tenner on it on eBay, but I’m going to drill out a blank panel and fit the screen behind the panel. It should look pretty boss.