Okay, I have a circuit I've been making for a while now, but it's a pain in the butt to solder 19 2N3904s with their 10k resistors every time I make a board. I've had some good experience with 2004ANs on other projects and want to use them for this one. Before I start etching PCBs though, I want to make sure I haven't made any huge mistakes.
The logic that drives the transistors has been tested extensively, so I haven't included it. There are 2x 4015's and a single 4017 being run with a 556 timer. The only change to this logic portion is to add 0.1uF caps to each 40xx chip (V+, GND). Also not included are the birds' nest of nets to wire into sockets that run out to warm white LEDS. Again, this portion has been tested and works.
The smaller image is what I have used previously as it pertains to logic coming into a transistor to power an LED (3-3.4V, 20mA). This setup was just repeated 19 times, each from a different logic pinout. The larger image is the section in question. I currently plan for 3x ULN2004AN, and have eliminated the 10k resistors, as those are in the array, and I'm using 470ohm resistor arrays in place of the original individual resistors. Testing of the original circuit showed acceptable performance for VCC between 6 and 15VDC, but I'm not sure if those limits are good for the longevity of the circuit.
To sum up, here are my questions:
1) Are my transistor arrays hooked up correctly to replace 2N3904s?
2) Is the ULN2004AN transistor a good choice, or is a ULN2003AN better for this application?
3) Do my allowable voltages for VCC allow for a stable/long lifecycle?
I'm not to do anything exotic, just reduce my parts count and assembly time but replacing similar individual components with arrays.
The logic that drives the transistors has been tested extensively, so I haven't included it. There are 2x 4015's and a single 4017 being run with a 556 timer. The only change to this logic portion is to add 0.1uF caps to each 40xx chip (V+, GND). Also not included are the birds' nest of nets to wire into sockets that run out to warm white LEDS. Again, this portion has been tested and works.
The smaller image is what I have used previously as it pertains to logic coming into a transistor to power an LED (3-3.4V, 20mA). This setup was just repeated 19 times, each from a different logic pinout. The larger image is the section in question. I currently plan for 3x ULN2004AN, and have eliminated the 10k resistors, as those are in the array, and I'm using 470ohm resistor arrays in place of the original individual resistors. Testing of the original circuit showed acceptable performance for VCC between 6 and 15VDC, but I'm not sure if those limits are good for the longevity of the circuit.
To sum up, here are my questions:
1) Are my transistor arrays hooked up correctly to replace 2N3904s?
2) Is the ULN2004AN transistor a good choice, or is a ULN2003AN better for this application?
3) Do my allowable voltages for VCC allow for a stable/long lifecycle?
I'm not to do anything exotic, just reduce my parts count and assembly time but replacing similar individual components with arrays.
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