I am building my grappel for my tractor and with everyones help on this site, I will be ordering this selector valve.
https://www.surpluscenter.com/item.asp?UID=2468021818355035&catname=&qty=1&item=9-5117-a
Do I need to install an electrical relay to power this valve?
It is custom and recommended to use a relay! They are inexpensive, and do a better job than a "cheap" switch. It also depends on how wiring can be designed.
THE LOW AMP CIRCUIT:
Use a small diameter wire, AWG20-AWG24, from a PLUS terminal, use fused power, either from fuse box or use an inline fuse (5A), from fuse to switch, from switch to coil on relay (Bosch 85), from coil on relay (Bosch 86) back to a good MINUS (or GROUND if good, secure ground is available)
Now the relay should be able to switch the internal contacts when you operate the toggle switch. You should be able to hear relay "clicking"...
THE HIGH AMP CIRCUIT:
Use a large diameter wire, AWG10-AWG44, from a PLUS terminal, use fused power (use the same fuse as the LOW AMP CIRCUIT), from fuse to switch in relay (Bosch 30), from switch in relay (Bosch 87a) to valve coil (Hirschman connector), from valve coil back to a good MINUS terminal (GROUND is not recommended for solenoids)
The purpose with the use of a relay is to remote control a large switch (high amps), with a small switch (low amps). That way we can use less expensive copper wire for the long remote switch. We also reduce the risk for VOLTAGE DROP in the critical high amp line to the coil
If so what should I buy, what specifications should I be looking for?
Buy a simple
Automotive relay 12V/30A for each coil on the valve, and a
simple toggle switch, 5A, for each coil on the valve...
Also get a
Protection Diode for each coil on your valve, mount the diode inside the Hirschmann contact. See my previous post about diodes...
where can i purchase this, perhaps an online site?
Surplus Center have the relays and the switches.....The Hirschmann contact should come with the valve....Wire you can buy at Napa or Chucks etc....Diode at Radio Shack...
BTW Both Napa and Radio Shack should have wire, fuses, relays and switches