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

Posted by pugzor 
[dumb question] Turn on fans at a certain current?
July 18, 2017 04:11AM
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.
VDX
Re: [dumb question] Turn on fans at a certain current?
July 18, 2017 04:52AM
... you can hack a temp-sensor for this - or read more about a "comparator" circuit: [www.learnabout-electronics.org]


Viktor
Re: [dumb question] Turn on fans at a certain current?
July 18, 2017 11:40AM
Some electronics/firmware combinations provide for turning a fan on when the CPU temperature reaches a certain value.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Full disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet.
Re: [dumb question] Turn on fans at a certain current?
July 19, 2017 12:19AM
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.
Re: [dumb question] Turn on fans at a certain current?
July 19, 2017 02:23AM
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...
Re: [dumb question] Turn on fans at a certain current?
July 19, 2017 10:32PM
That makes sense, although it would also work without SSR. Just put the PSU enclosure fan(s) parallel to the extruder fan grinning smiley
The fan driver can stand it easily.
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