BATC Forum

Hi,

There is the option (I read) of a fan.

Now looking at the PCB and measuring the PCB PNG holes and scaling, together with the suggested RPi4 spacer length of 20 mm leads me to have assumed a 40 mm fan with about a 10 mm thickness. Much more and it raises the RPi off the 40 way header that is about 16 mm in depth.

Now the BOM does mention using a dropper resistor for various fan voltages so I am guessing, again, in the range of 5V to 12 V.

Perhaps a little size clarity would help so the fixing holes may line up.

I took the plunge and went for a 40 mm 12 V one on 32 mm square fixings.

I maybe wrong...

Addendum: I missed this snippet "providing clearance for a 40x40x10mm fan". So perhaps someone else will too. I think a BOM entry would help.

73, Mike

G0MJW is looking after the pcb, so I'll let him give the definitive answer on fan sizing.

The fan supply on J3 is 12v through R1, so a 12v fan with a resistor to modify the speed should be fine. R1 is 2512 size, but I expect 2 x 1206 size resistors in series would work.

5v, without a series resistor, is available on JP4, just to the east of the 3 psu modules.

Brian

Thanks Brian,

All noted. Just got some parts today, including 40 mm X 10 mm fan, part number 281-6685 from Farnell.

Its really a matter just to add a BOM line item [reminder] with the definite fixing hole size so anyone can order one that screws in OK.
Otherwise there maybe a mechanical problem.

Thanks, Mike

Winterhill is an advanced project with decisions like the casing and cooling left largely to the builder. We assume a fairly high level of construction experience. The solutions can be shared and added to the Wiki over time.

The PCB fan, if fitted, is indeed a 40mmx40mmx10mm standard 12V fan. The dropper resistor is needed to slow it down, both in order to keep the operator sane, and to account for 13.8V supply if used. I used 100R and it was fine, but fans vary in their current ratings. The reason a specific fan is not on the BOM is I have not bought one, so I don't know what to choose.

This is not the only option. A case fan could be used, it depends on how you box it and how you cool the PI. My first prototype used a heatsink case for the PI and the fan just ensures airflow in the repurposed set top box it resides in. I will post some pictures of how I have done it.

Mike

Fine by me,

Thanks for the information.

My comments are based on the ease of a simple translation from BOM to an order, and not having items in the BOM meant I was missing a couple of items. I like to order up all the components in advance (of the disappointment in missing something important later).

And the fan [if used] has to fit into the PCB as supplied - and the mounting holes are 32 mm square. But this is not specified.

Thanks for the update, I am still waiting for the BATC order and Farnell but have built the SD card already. The software instructions provided made that easy, ta.

73, Mike