I am connecting several relays to a PIC (16F817) and am having trouble getting it to work reliably. The performance of the electronic circuitry is degrading. I did a search in the forums here and found a lot of good information but I have some questions about what I have read. First, I saw a recommendation that the diode on the relay coil be a 1N4006 (PIV 800 V). I am using a 1N4002 (PIV 50 V). Am I using the wrong diode?? The relays have 24 VDC coils.
Second, someone suggested adding a little capacitance (330 pF) across the coil to give the diodes time to turn on. This is the first that I have heard of this (certainly not an expert in the field but found it interesting that I hadn't heard of this before). Will this make the circuit more reliable??
Third, I am using a 2N2222 transistor to control the relay. The (-) of the relay is connected to the collector (+ of relay to 24 VDC), emitter to ground and the base is connected to the PIC through a 2.7KOhm resistor. The relay coil has a resistance of 2880 Ohms. Does anyone see any problems with this??
Lastly, I have 47 uF, 35 V capacitors on either side of the 7805T.
I have made some changes to the design since I did the schematic and I won't be able to update the schematic for a week or so but I was hoping the description above would be sufficient. Any suggestions for improvement to the above would be appreciated.
Second, someone suggested adding a little capacitance (330 pF) across the coil to give the diodes time to turn on. This is the first that I have heard of this (certainly not an expert in the field but found it interesting that I hadn't heard of this before). Will this make the circuit more reliable??
Third, I am using a 2N2222 transistor to control the relay. The (-) of the relay is connected to the collector (+ of relay to 24 VDC), emitter to ground and the base is connected to the PIC through a 2.7KOhm resistor. The relay coil has a resistance of 2880 Ohms. Does anyone see any problems with this??
Lastly, I have 47 uF, 35 V capacitors on either side of the 7805T.
I have made some changes to the design since I did the schematic and I won't be able to update the schematic for a week or so but I was hoping the description above would be sufficient. Any suggestions for improvement to the above would be appreciated.