I posted this some days ago on Projects but had no responses: Trying again on this series:
I'm currently using the attached circuit to drive a relay when finger contact is made between points A and B. Maximum current across contacts must be less than 1 ua (assuming very low finger resistance or short across A and B). The circuit as shown works but I have several questions:]
1. What is the effect of inc. or decreasing relay coil resistance on battery drain?
2. Are R2 and R3 optimal values?
3. MOST IMPORTANT ISSUE: Can I use a NPN Darlington to replace the two 2N2222 transistors? If so, which Darlington would you suggest and would this affect choice of the R2 and R3 resistors?
Many Thanks,
BurtS
I'm currently using the attached circuit to drive a relay when finger contact is made between points A and B. Maximum current across contacts must be less than 1 ua (assuming very low finger resistance or short across A and B). The circuit as shown works but I have several questions:]
1. What is the effect of inc. or decreasing relay coil resistance on battery drain?
2. Are R2 and R3 optimal values?
3. MOST IMPORTANT ISSUE: Can I use a NPN Darlington to replace the two 2N2222 transistors? If so, which Darlington would you suggest and would this affect choice of the R2 and R3 resistors?
Many Thanks,
BurtS
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