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Discussion Starter #1
I'm thinking about experimenting with a Pro mini to manipulate the PWM signal on the DCDC 'DVCT' line. The Pro Mini can take up to 12V input. What would be the simplest way to power the unit? Is there a good 5V source in the IMA compartment? Could I use a voltage divider to drop the 12V system voltage a bit? Maybe I'll need or should use a buck converter?
 

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Discussion Starter #2
Here's a little sleuthing on the 'voltage divider' idea. I read at Sparkfun tutorials that you shouldn't use voltage dividers as power supplies - which I already knew. But, I was thinking the current should be quite low and that it might be OK. Sparkfun concludes with this: "Basically, don't use a voltage divider as a voltage supply for anything that requires even a modest amount of power."

I'm not sure what "modest" is, though. The Pro Mini power consumption is 40mA per pin, and I'll only need 1 pin, maybe 2. So call it 80mA.

My 12V system will be at about 14V and I think I'd like to drop it to 10V. I can do that with a voltage divider where R1 is 100Ω and R2 is 250Ω.

With a drop of 4V and a current of about 80mA, my R1 resistor will need to dissipate 4V * 0.08A= 0.32W, I think...

So, this doesn't sound too serious to me, maybe a 1W resistor? Are my calculations right/appropriate, am I missing something?
 

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Yes, even that is a modest amount of power. Might work if you got lucky, but it'll still be a poor idea.

The best bet would be to get a 12V to 5V regulated supply. You could roll your own solution with a linear regulator. Something like this, or this . Don't forgot the filtering caps as specified by the datasheet.

Alternatively, get something premade. Something like this, although it would be massively overkill.
 

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Here's some cheaper options, if you don't mind waiting for a shipment from China:

https://www.ebay.com/itm/123048446165
https://www.ebay.com/itm/401327863545
https://www.ebay.com/itm/173257198439
https://www.ebay.com/itm/172855717087

You can also get these from US suppliers on eBay for a few more bucks, if you're in a hurry. I've heard these "buck converter" power supplies cause radio interference. The simpler voltage regulator type might be better. They're less efficient, but at the low current draw of an Arduino, who cares?
 

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From the BCM Interceptor thread

"The 5v power for the Interceptor is sourced from the MCM by splicing into

MCM Connector C Pin 24 Grn/Wht (+5V)
MCM Connector B Pin 25 Red/Yel (Ground) "

Might work if the Arduino current isn't too great.
 

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Okay I'm someone who has tried to install I want to say 6 or 7 Pro Minis or clones thereof into various Insights in the IMA bay... the best advice I have is don't do it. Go with an Arduino with an onboard 12v --> 5v converter such as an Uno. Buck converters off of Ebay are not the highest quality.
 

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Discussion Starter #7 (Edited)
Lots of great advice, thanks to you all...

I bought some inexpensive buck converters a while back, I'm using one of them to power a PWM signal generator to manipulate DCDC output voltage. Both devices sit on top of the DCDC converter, no problems that I can tell thus far. Here's a pic of that setup (in preliminary form):


Natalya, what problems did you run into with Pro Minis in the IMA bay? Despite your warning, I might just go ahead and do it, because this is more of a learning project than anything practical. The PWM thing I mention above does what I need (for the most part). Trying the Pro Mini is more about just figuring out how to work with this kind of stuff...

Also, do you recall if the Pro Mini can do 0-5V PWM if the input power is only 5V? It'd be... convenient if I could take power from the location Jime mentions...

Oh, also, you say this:
....Go with an Arduino with an onboard 12v --> 5v converter....
I was under the impression that the Pro Mini does have a converter onboard. The specs say this about the power supply: "Board Power Supply: 5 - 12 V (5V model)." I thought that meant the supply could be anywhere in the range from 5V to 12V? Here's another description of the power supply: "There is a voltage regulator on board so it can accept voltage up to 12VDC. If you're supplying unregulated power to the board, be sure to connect to the "RAW" pin on not VCC."
 
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