speedorhaste
New Member
Here's what I have done so far, and questions / comments I have:
The schematic is probably a bit busy but it passes all circuit tests. I have used Eagle software to do this. Any comments would be welcome. I have tried placing this schematic onto a board in Eagle. Now that is a challenge!
- I have re-directed the caps from the reset pin to go to active power supply. Hopefully I have them around the right way!
- Diodes quoted in most places are 4148, but I think they should be higher rated (e.g. 4001)
- The 4004 fly back diodes for the relays are way over spec'd, but the parts library I drew this from does not have lower rated diodes!
- Not sure if I need a current limiting resistor to feed the base of the transistors. I don't have specs for the relays as yet, but I could assume the base needs at least 1 milliamp to turn it safely on. The Q output only puts out around 3 milliamps.
- The relay set up might need some explanation. I have used DPDT, using one of the poles (say pole B of relay B) to switch power to pole A of relay A, pole A doing the primary switching to the roof ECU. This is just to ensure that power is not available to the relay that is not being used.
The schematic is probably a bit busy but it passes all circuit tests. I have used Eagle software to do this. Any comments would be welcome. I have tried placing this schematic onto a board in Eagle. Now that is a challenge!