[dumb question] Turn on fans at a certain current?

Hi guys,

This is a really dumb question and I'm 100% sure I'm just thinking about this the wrong way.

Is there a device out there that would act as a relay when current draw hits a certain amount? Kind of like a current-sensing relay/switch?

Problem I'm trying to solve - I'd like to build separate enclosures for my power supply and other electronics (just to make them more accessible for upgrades/repairs/etc rather than fitting them to the frame). A nice to have would be to kick in the fans for these enclosures when a load more than idle (I'm going to say less than 500ma @ 24vdc) is detected.

Thanks.

... you can hack a temp-sensor for this - or read more about a "comparator" circuit: [www.learnabout-electronics.org]

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Some electronics/firmware combinations provide for turning a fan on when the CPU temperature reaches a certain value.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Wouldn't it be the easiest to wire the PSU enclosure fan parallel to the bed heater? Most PSU can stand the power required by the extruder without cooling.

Thanks for your answers everyone!

Think I was probably over complicating things. I was thinking about it and really the one component that's always drawing current when the machine is in operation would be the extruder cooling fan. Easiest solution to this would be to connect a SSR up to that, wouldn't it? It wouldn't matter the speed the fan was running at.

Objective was to actively cool both control board and PSU when the printer is in operation (not idle) and I think this would achieve it...

That makes sense, although it would also work without SSR. Just put the PSU enclosure fan(s) parallel to the extruder fan
The fan driver can stand it easily.