My soldering is probably the cause
I’m using a regular 25-30W soldering iron without temperature control. Heating the wire/pad until the solder is melted and then let go.
I might have soldered the LED wrong also, but if M is connected to LED cathode there should be continuity between “+” and “m” on the mosx when measure through the LED? Like in the photo:
Don’t know if this is usual, but the LED lights up when I use my voltmeter on continuity setting so I know the LED is working at least. Just like in the picture when I measure between + and m.
And at first I did connect battery and all and discovered I wasn’t able to adjust brightness or enter setup mode. The LED was running direct drive I guess. Luckily the battery wasn’t full and I jused just thin wires to test with. It was bright
The LEDs are a XHP70.2 6V on the mosX connected in series with a XHP50.2 6V on separate pcb. Driven by 4 samsung 18650 batteries in series. The driver is the 4s/6A version.
The curcuit seems to be fine when the gate wire is not connected between driver and mosx. When this wire is connected it seems like the FET is shorted or connected somehow, like this:
Try to measure exact resistance (instead of continuity) between + and M pads, with LED should still see high resistance. Best way to set LED is to set multimeter to diode test, if LED is ok it will emit some light, but that usually only works for 3V LEDs.
Since you are running 2 LEDs on separate PCBs, how did you connect those PCBs? Diagram for one LED looks ok.
I followed this video on how to flow the LED onto the mosx. Only difference was that I did it in the kitchen using an old frying pan (don’t use it for cooking anymore ).
Used low temperature solder paste. I don’t think the solder on the fet melted while I did it.
Yes it is. Input voltage on the driver is 16V. Two series LEDs in series.
Maybe I should switch them around so the mosx is closest to ground?
But this was my next question: do I need to hook up the battery for the FET to function? I thought it was normally open curcuit. A bit scared to power on after yesterday when I think it was direct drive…
FET is normally open (high resistance) but if gate pin is free floating it can be charged for example via testing with mulitmeter and FET will be in closed (low Ohm) state for quite a few seconds even without any voltage applied to gate becasue of gate capacitance.
Actually this is the way I test mosX boards with FET: I charge gate by applying x.xV for 1-2sec, and then I connect mosX board with LED to power supply to + and - pads like standard (non mosX ) MCPCBs.
At 3Amps per LED they are within rated manufacturer current which means they would be ok even on ultra cheap standard dielectric MCPCBs, so black mosled 4x is more than fine.
Ldb4 hv 6A driving 1 xhp70.2 and 1 xhp50.2 in series off a 4S battery. CNC milled housing in aluminium for good thermal properties. 3d printed gopro mount. And remote control of course. Looking forward to try it on the trails :D