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5

The problem you have is one that is a design problem. You need to realize that the three LEDs in one string may very well have a higher total voltage drop than the three LEDs in the parallel string. The ones with the lower voltage drop may light while the others do not. Since you do not have any intentional current limiting scheme to control the current ...


3

Basically, a LED is just a diode. If you take a diode and bias it in reverse, no current flows through, because there's no hole/electron recombination happening. Now, that "no" is a bit of a stretch: of course, due to thermal effects, pure luck (tunneling), a few electrons and holes will still recombine. Now, in an LED, a photon hitting the carrier-...


1

Use a good ol' BJT, or find a logic-level FET rated for 1.8V. I've called out a 2N3904 in the suggested schematic below, but (A) you can use just about any small-signal NPN there, and (B) there are prebiased transistors that'll work and save you a resistor. Design for an 0.7V drop from base to emitter, and a base current of about 1/10 of your desired ...


1

The problem is most likely that the mosfet does not have enough voltage to fully turn on. Vgs is probably not high enough. I couldn't find the datasheet for the CMPD7002 (or any part named that). First make sure the Vgs will give you enough current, find how much Vgs you need for the Rds on. You'll need to do one or more of these things: 1) If the GPIO's on ...


1

Here is what I have done based on that arduino forum response. I have computed the values from 0 to 255 so it's easy to use with pwm on arduino byte ledLookupTable[] = {0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,6,6,6,7,7,7,8,8,8,9,9,9,10,10,11,11,11,12,12,13,13,14,14,15,15,16,16,17,17,18,18,19,19,20,20,21,21,22,23,23,24,24,...


1

ESD protection is needed if the design comes in contact with objects that have high voltage potentials (like humans). If you think people will be touching the LED's or the cable, then protect the circuit. I'm not sure that LED's are susceptible to ESD damage as other parts. At any rate, if your worried about it a TVS diode across the power terminals would ...


1

According to the datasheet, the SN74AHCT138N is not qualified for output currents greater than 8 mA. If your LEDs truly are 5 V devices (in that they have current limiting built-in), what is their typical operating current at 5 V? As the CMOS output current demand increases, the output voltage rises above GND, decreasing the voltage across the LED. As ...


1

You haven't got any of your enable pins connected. You should have pull downs on your inputs.


1

those LED modules are so close together that there's no room to add junction points for cutting it. just cut the strip using a hacksaw (or whatever works) and solder your three wires to the existing solder on the component leads. secure the wires with 2 part epoxy or cyanoacrylate glue. the red wires are the power wires and should be thich-ish wire the ...


1

I think the toroid winding shorts the power supply as it happens with my buck converter. The toroid should not be connected so that it shorts the power supply. If the red and black wires are going to the battery, then you've wired it wrong. What you have in the photo doesn't match the circuit diagram. I can only guess as to which lead from the transistor ...


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