Hi TVRON, I was hoping you could help me out by figuring out the connection methods or propose some ideas for autothrottle circuits. But first allow me to explain you my situation. Few days ago I went to local electronics store and bought 4 relays. Until I was ready to build the circuit I realized I got 2 wrong relays. I got is DPDT instead of DPST. So I went back to electronic store and asked that sales person to replace relays from DPDT to DPST. But unfortunately he doesn't have DPST in stock, and he made an additional comments stating that DPDT can still work like DPST if making only one connection. So I showed him the schematic that you created by printing it out on my printer... he said that since it has two DPSY relays for seprate motors that sinle DPDT can still do function as if its two DPST... so I was not sure if he was correct.. can DPDT works same way as two DPST? if so let me know. I have already attach picture of DPDT relay schematic in case you want to observe it.

According to your relay circuits, would you have an explaination of how SPST,DPST, Diode and etc works... because I could not once understand how these works... Thanks

Hi Arthur.Sorry about the delay but I have been out of town.Yes a DPDT would work... Maybe I am saying it wrong. in my symatic, the small relay has just one set of contacts. It is just a switch. with no power it has a contact to pin 1 and 5. with power on, it has a contact to pins 1 and 6. We say it has a NC and a NO set of contacts. NC = normaly closed. NO = normaly open contacts. pin 1 is the common pin. 5 and 6 are the two poles. with power off, pin 5 will have the 3 vdc on it however, pin 5 is not used. Now with power on pin 6 has 3vdc on it. Now the large relay has two sets of contacts and two common pins. with power off, pin 8 would contact pin 4 and pin 7 would contact pin 3. with power on pin 8 would contact pin 2 and pin 7 would contact pin 1. pin 1 and 4 are tied together and pin 2 and 3 are tied together. OK now how this all works. with epic set point 4 on or going to ground the small relay is entergized. voltage flows from +12vdc thru the relay coil and to ground in the 32 point card. the diode is there to keep any induced voltage from feeding back. anytime you have an inductor, which is what a coil is, you should use a diode. with the small relay entergized voltage flows to the large relay pins 1 and 4. pin 8 is contacting pin 4 and voltage flows to the servo, thru the servo and out to pin 7 which is contacting to pin 3 which goes to ground. the servo motor run clockwise. now if you set epic setpoint 3 the large relay is entergized and pin 8 is contacting pin 2. pin 7 is contacting pin 1. see now the servo turns counter clockwise. I hope this made it clear Ron.