My team recently just purchased a second VH-109 radio, so we can convert it to a VH-113 access point. I noticed that they were saying that the only real difference between the VH-109 and the VH-113 is that they have added a fan for cooling. So naturally, I tried to figure out a way to cool our radio without running additional power wires. My first thought was just using POE to power a 12v fan, which works fine. However, I did notice that if you power the radio via POE, the 12v dc input actually is outputting 12v, and can power the fan. I wanted to post this find to see if anyone can help either reassure or tell me that this is a terrible idea. Thanks.
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Doesn’t sound like the most terrible thing to do… I don’t know what would happen if things were miswired but in the configuration you described it should work fine.
Regarding the legality, I guess we’d have to wait for the new manual.
That’s how we’re powering fans with the heatsink solution.
Additionally, the VH-113 just has a fan soldered into the Weidmuller port internally.
If you did this on robot, the fan would be exposed to potentially high back EMF voltages without protection, but, you wouldn’t do that, right? 
The only thing I can think of note are:
- Don’t do it on a robot. I’d be a bit surprised if it wasn’t rules-illegal.
- Electrically it’s fine enough, but if your power source is unregulated (e.g. a battery) or not 12V, your fan’s power source will also be. Whatever voltage you’re providing it is what you’re getting out.
- As such, don’t use a REV RPM to power it, it outputs 18V.
- Avoid powering straight off of a battery, especially if motors are also connected like on a robot.
I was not planning on doing it on the robot, because I plan to modify the case for better cooling. It would only be used for the VH-113 mod. I may even toss a diode in there to be extra safe.
The diode is probably overklll, especially if you’re doing it off robot.
You’re safe to just plug the fans into the Weidmuller 12V input.