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The remote is an open drain output from the camera, which basically sinks to ground. The pull-up on the board sets the potential. Whether I’ve done that correctly or not I’m not 100% sure of. I have a scope but I’m no scope wizard. I take it this would be adjusted with the pull-up resistor on the gate
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According to this:
https://www.infineon.com/dgdl/mosfet.pdf?fileId=5546d462533600a4015357444e913f4f , on the section called "GATE CHARGE", the way to calculate the turn on time, is based on the gate charge. Take notice of the following paragraph:
The advantage of using gate charge is that the designer can easily calculate the amount of current required from the drive circuit to switch the device on in a desired length of time because Q = CV and I = C dv/dt, the Q = Time x current. For example, a device with a gate charge of
20nC can be turned on in 20 μsec if 1ma is supplied to the gate or it can turn on in 20nsec if the gate current is increased to 1A. These simple calculations would not have been possible with input capacitance values.In this datasheet, they specify 223 pC of "Total Gate Charge", so let's suppose that you want to switch this in 10 us, then current = Q/time = 223 pC / 10 us = 22.3 uA . Doesn't seems difficult to turn on at all.
A simulation seems to agree in that you should have short times to turn the state of the mosfet (see attachment). Of course,
The fact that the LDH-45 has analog and a PWM dimming could mean that the PWM input is just turned into a voltage internally, as others have already mentioned. Also take notice of the voltage limits on the PWM and Analog dim inputs, that seem to be exactly the same, so that further suggests that they're related. And they don't specify the time to turn on. Also, take notice that there is a graph that shows "output current vs PWM dim input", so, it isn't turning the leds on and off with the PWM duty cycle, but just modifying the output current according to it.
It seems quite possible that the LED drivers themselves are just slower to turn on. You can check that with an oscilloscope. Tie one channel to the PWM dim input, and the other to Vout. That way you can check how much time it takes the output to rise after you enable the driver. You should be able to do that with a digital scope with the trigger in manual mode, using the PWM dim input as trigger. (VOUT- is the same than GND? otherwise you could have trouble trying to measure the output, see Dave's video on "how to not blow your scope").
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That's very informative and thanks for verifying the validity of the passives, I didn't quite get a chance to wrap my head around Spice yet. I haven't had a chance to play with the scope yet, I really only use it for verifying the switching of proximity sensors on tooth wheels and encoders and checking for noise, but I will get into it as you suggested if I continue on this route. This board as is seems more feasible now that I've worked the lighting a little better to accommodate the lower voltage output of the LDH compared to the AC-DC driver. I'm down to about 460us which is probably acceptable, my only small gripe is that there is a very slight change in light output between camera frames. Again it's something that wasn't seen on the AC setup but I'm sure it has to do with slight inconsistencies in the LDH driver while using it in this way. Not quite a dealbreaker yet though.
I did breadboard an SMD SSR to test the LDH for switching the output and this looks like a pretty big fail, which is probably why the PWM, On/off function exists in the first place. Unilike the AC-DC drivers the LDH drivers do not recover the output well at all while being switched so that's not an option. I did consider ealex's comment a little more but it still seems it would be an issue having to pull 48v DC out of something.......Then it dawned on me that I've been a bit narrowminded again because of all the different turns I've had to take with this whole project. I use 12 LEDs wired in series on a PCB I had fabbed based on Testing with the previous methods and that works well. Not sure Why I didn't figure sooner that I can achieve the same thing running them in a series/parallel combination at 24v. I modified one of the LED PCBs for this. I still like trying to switch them with an Opto for isolation so I'm going to play around with that and see how that turns out.