Step one. Bought the van.
Hello Everybody, First post. I camp a lot in tents but after spending three days straight in a tent in the rain at Dolly Sods I swore I'd make a change. Here it is. Bought it Wednesday. Dro...
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After I installed a new radio I wanted to add a switch so I could choose to run the radio from the house batteries or the starting (van) battery. I've set it up so there is a singe SPDT momentary ((on)-off-(on)) switch that selects either power source. Once switched the radio runs completely off the selected source and draws no power from the other source. Not only does the radio not lose it's memory setting when switching between the two sources but if it's playing a song there is no audible clue that anything has changed.
To do the actual switching I'm using two 12 volt relays. These relays are rated for 16 amps while the radio is only fused for 10 amps so they should be robust enough. The relays are a dual coil latching type. Since they are latching, no power is required to keep them in the selected position after being switched which is different from a regular relay. That saves power usage and it's why I only need a momentary switch to activate them. I bought the relays for $4.66 each from Digikey. Here's the link.
The relays are made to be mounted to a circuit board. So I first drew up a schematic then soldered the relays to a small piece of stripboard which is type of prototyping circuit board. After soldering on the relays I added connecting wires.
After finishing with the soldering I was thinking of a how to protect the exposed wiring on the circuit board since it will be installed inside the dash. Thought about building a small plexiglass box when I had a "what if" idea and went looking for an old prescription bottle.
Son of a gun. It fits as if they were made for each other. I'll have to remember this idea. I added a couple vent holes to the bottom of the bottle.
Add connectors to all the wires. The connector is male or female depending on if it's hot or not.
For the circuit to work as planned I'll need a "hot on start" power source. According to my Ford EVT manual the plug that goes to the back of the stock radio should have such a wire. I looked and it doesn't. So trace the circuit back to the next connector which is number 201 located in the right kick panel of the passenger foot well. There are other connectors in the same area.
To work on the connectors use pliers to remove this black plastic pin.
That allows the connectors to swing out.
This must be connector 201 since it's the only one with this shape.
I'm interested in circuit #1000 which is a red wire with black stripe. Must be this one.
Cut the wire then check that it's hot on start. It is. The circuit dead ended at the connector so I wasn't too worried about cutting the wire free.
Put all the connectors back like I found them then run a new "hot on start" wire into the dash. Integrate the wiring into the radio plug adapter (right white) I used to plug the stock radio plug into the new radio plug (left black).
Here's the diode I use to stop switch selected coil voltage from back feeding to the starting circuit.
Here's how it works. When the van is sitting and not running the radio is dark. If I flip the switch down to "House" the radio lights up now being powered by the house battery. It's a momentary switch so the toggle snaps back to the center. The radio will stay powered from the house battery until I either flip the switch to "Van" or start the van. When I start the engine the radio automatically switches back to the van battery. That way I don't have to worry about switching the radio back to van and since it's a momentary switch I can never leave it in the wrong position. A rather bad habit of mine.
After I got everything wired up it actually worked right the first time. Surprised the heck outta' me. Well almost right. I'd wired up House and Van backwards on the switch but that's easy to fix. Just rotated the switch 180 degrees.
In practice I've found a neat use I hadn't planned on. When pulling into a parking spot and there is a song on the radio I want to hear the end of I just flip the selector switch to "House". Then after I turn off the ignition the radio keeps playing without missing a beat. It's now become a gas saving feature.
To do the actual switching I'm using two 12 volt relays. These relays are rated for 16 amps while the radio is only fused for 10 amps so they should be robust enough. The relays are a dual coil latching type. Since they are latching, no power is required to keep them in the selected position after being switched which is different from a regular relay. That saves power usage and it's why I only need a momentary switch to activate them. I bought the relays for $4.66 each from Digikey. Here's the link.
The relays are made to be mounted to a circuit board. So I first drew up a schematic then soldered the relays to a small piece of stripboard which is type of prototyping circuit board. After soldering on the relays I added connecting wires.
After finishing with the soldering I was thinking of a how to protect the exposed wiring on the circuit board since it will be installed inside the dash. Thought about building a small plexiglass box when I had a "what if" idea and went looking for an old prescription bottle.
Son of a gun. It fits as if they were made for each other. I'll have to remember this idea. I added a couple vent holes to the bottom of the bottle.
Add connectors to all the wires. The connector is male or female depending on if it's hot or not.
For the circuit to work as planned I'll need a "hot on start" power source. According to my Ford EVT manual the plug that goes to the back of the stock radio should have such a wire. I looked and it doesn't. So trace the circuit back to the next connector which is number 201 located in the right kick panel of the passenger foot well. There are other connectors in the same area.
To work on the connectors use pliers to remove this black plastic pin.
That allows the connectors to swing out.
This must be connector 201 since it's the only one with this shape.
I'm interested in circuit #1000 which is a red wire with black stripe. Must be this one.
Cut the wire then check that it's hot on start. It is. The circuit dead ended at the connector so I wasn't too worried about cutting the wire free.
Put all the connectors back like I found them then run a new "hot on start" wire into the dash. Integrate the wiring into the radio plug adapter (right white) I used to plug the stock radio plug into the new radio plug (left black).
Here's the diode I use to stop switch selected coil voltage from back feeding to the starting circuit.
Here's how it works. When the van is sitting and not running the radio is dark. If I flip the switch down to "House" the radio lights up now being powered by the house battery. It's a momentary switch so the toggle snaps back to the center. The radio will stay powered from the house battery until I either flip the switch to "Van" or start the van. When I start the engine the radio automatically switches back to the van battery. That way I don't have to worry about switching the radio back to van and since it's a momentary switch I can never leave it in the wrong position. A rather bad habit of mine.
After I got everything wired up it actually worked right the first time. Surprised the heck outta' me. Well almost right. I'd wired up House and Van backwards on the switch but that's easy to fix. Just rotated the switch 180 degrees.
In practice I've found a neat use I hadn't planned on. When pulling into a parking spot and there is a song on the radio I want to hear the end of I just flip the selector switch to "House". Then after I turn off the ignition the radio keeps playing without missing a beat. It's now become a gas saving feature.
