Hi, I think you may have a problem with supply and filtering, you mentioned that the supply to the array with the mosfet relay was down to 3.2v.These arrays have micrcontrollers built in them, probably running at 3.3V. If the main supply drops to 3.2V then the regulation will not be available to keep the microcontroller stable.To fix this either use a small mechanical relay, or parallel up the output of three or more of these mosfet relays units to drop the switching resistance.To check, measure the voltage across pins 3 and 4, AT THE opto mosfet relay and see if you are loosing the 1v there and not your wiring or too small width tracks to the opto mosfet relay.Tom
Try it as a low-side switch instead of high-side?I haven't worked with MOSFET relays like that, from the datasheet I assume pins 3 and 4 would be interchangeable, but I might also try swapping them around.
How about just a MOSFET? Since you're tying the grounds together on the two sides of the opto device, I assume isolation really isn't necessary.
How about just a MOSFET? Since you're tying the grounds together on the two sides of the opto device, I assume isolation really isn't necessary. The MOSFET part in the schematic will switch 5-6 amps, has RDS(ON) of 27m? @ VGS = 2.5V, and is in an SOT-23 package.
So "just a MOSFET" he says ... All of the high Amp MOSFETS I find are large packages and I don't have the physical space for four of them.
Yeah, that'll work ... bit of an overkill on the voltage, but that's fine. It's only switching 4.2V (max, nominal is 3.7V, minimum will be 3.0V). Signal will be same voltage (range).
Is there a through hole counter part? I like doing breadboard testing before I commit an SMD design for manufacturing.
Ok, so assuming pin 1 on the strip is VCC and pin 4 is GND, is this the proper configuration, or do I need to turn things around?
And how did you calculate what the value of R2 should be (you have it as 220 in your schematic)?