SparkFun Forums

[Mr.UNOwen]

So I have a mosfet circuit to control a group of 6 fans. At full blast, there's no issue, but when at a lower duty cycle, LEDs begin to flicker and motors begin to stutter that aren't part of that mosfet circuit, but share the 12v line. Initially I thought this was a similar problem that relays have and added a diode from gnd to 12v (from the fan connection side), but no changes were observers. Does anyone have a clue what I'm missing?

Here's a link to the mosphet board: http://www.ebay.com/itm/301575487589?_t ... EBIDX%3AIT

[tradlost]

Yes, a full schematic is what you are missing. Then someone can help you.


Skickat från min iPhone med Tapatalk

[n1ist]

Sounds like your 12V source isn't stiff enough. I'd try adding some bulk capacitance to the rail.
/mike

[Mr.UNOwen]

That partly fixed it. I added a 1mF capacitor (across the voltage rails) and saw that it improved things. What fixed it entirely was having the diode go from 12 to the fan rather than across the fan connection (as well as keeping that capacitor on the voltage rail). So rather than having the diode draw down the spike, it'll just wall it off from the 12v source. From a heat stand point, this layout is running cooler, the other layout was producing a good amount of heat.