I've made an irrigation timer, which will be about 20mtr from the DC solenoid valves. I've been told the snubber diodes should be placed close to the valves, otherwise the cable will generate RF interference. The valves will be outside in a garden, and while there will be a cover the whole area will often be damp, so I'd prefer that the diodes were inside in the dry. I'm hoping to suppress the RF interference by turning the solenoid off slowly. I've attached a pdf of the circuit below.
IRLZ44N Pinout, solenoid circuit 2.pdf (73.5 KB)
This is the same as the circuit JimD gave me a while back, except for D2, R3 and C1.
The intention is that C1 will charge up reasonably quickly through the diode when the solenoid turns on, but it will discharge slowly through R3 when the solenoid turns off. I don't have much experience with electronics, will this work? I've suggested a value of 10 Meg for R3 because I want to keep the size of C1 down, but what would be appropriate values for the resistor and capacitor? The solenoids are 12v DC and draw about 2 A. The valves are direct acting, no pilot valve.
I don't expect the slow voltage decay will be a problem for the valves, but if someone wants to suggest otherwise I'm all ears. I'm thinking maybe 200 m/s to a second for the decay?
Thanks John