Quote:
Originally Posted by BrandonMods
What would you recommend for the voltage source? I might be able to get my hands on a DC power supply but there are no guarantees on that one. Any other ideas would be appreciated.
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Anything that results in a regulated 5V will work. At various times I have used: the USB adaptor, both wall plug and cigarette lighter ("12V") powered; a superfluous non-USB phone charger with the tip modified, wall plug powered; a bespoke, "12V" powered, 7805 based regulator circuit on perf. board with noise filtering (a web search will bring up any number of schematics for these); a spare ECU with just the power (plural) and ground wires connected, using one of the 5V reference outputs.
"12V" came from a car cigarette lighter, an SLA battery or a DC bench power supply.
You do need to be careful with the polarity with all of them.
Quote:
Originally Posted by MobilOne
Why not just put a small current 12v bulb in parallel with the fan motor? Why make it complicated?
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Careful with incandescent bulbs as they can draw a significant amount of current. On the fan side of the relay it is probably a tolerable fraction of the motor current. An LED (and resistor) is just as easy and will draw only a tiny amount of current, definitely a negligible current relative to the fan. (Don't even consider an incandescent bulb on the switching side of the relay.)