How could I keep the Radio in my truck from losing it's memory?

Question

Alright, I drive a tractor trailer for a freight company. Of course, there are no radios in the truck. What we(drivers) do is build a box with speakers and a car radio mounted in it. There are bannana plugs on the dash to get power from. Now The only problem is that everytime you shut the truck down the radio will lose it's memmory (presets, Volume level, etc). I could get an analog radio but that is just out of the question. I was thinking more along the lines of a secondary power source. Like connecting a 9V battery connector to the memmory wire so when the truck is off it will still hold it's memmory. Seeing that the radio won't work without this wire being hooked up to the trucks power I would have to incorporate a diode of some sort so I don't fry the battery. What kind of diode should I use and Where should I put it in the circuit? Thanks for any info....

I am not allowed and nor do I want to screw with their truck at all. Then I would be getting blamed when it wet down. So whatever I do has to be confined to inside that box. The switching diode sounds pretty good, I will definitely check into that.

Answer 1

Although I do think the 9 volt battery would work, I am not sure how much current the memory circuit uses. If the current draw is too high, the battery would not last long. You might consider a large enough AA battery holder to make up a 9 volt pack.

Also, you would need two diodes. One would go from the truck power to the radio's memory wire. The other one would go from the 9 volts backup power to the memory wire. You need two diodes to isolate each of the power sources. You don't want the truck power to feed into the 9 volt backup and vice versa.

Answer 2

I don't think that a 9v battery would work. You can find battery packs designed to hold 8 AA batteries, that you could build into your box; that would give the radio a 12v input. A basic 1 amp diode would be fine; just wire it inline on the wire from the battery pack that connects to the constant power input (yellow) at the back of the radio.

Another option would be a small, sealed lead-acid rechargeable 12v battery. This wouldn't need a diode; it would be recharging while you drive. This type of battery is available for about $10 from home security supply web sites. Even a small motorcycle battery would work, if you could secure it in the box; it would be more power than you need, but would be easy to find in a store.

Answer 3

I think the whole 9 volt / diode thing is throwing you for a loop. You should be able to buy a low amp, light weight, rechargeable 12 volt supply at a Radio Shack that could be built into the portable box.

Most newer radios and stereos have two separate power supplies. One that actually powers the unit and another for memory. (possibly another for power antenna) I don't think 9 V will do it. Direct current batteries operate on 2 volt cells. Generally even one dead cell will cause these devices to lose their mind.

Or, since this is portable, have the "constant power or memory" wire connected direct to whatever source (assuming you're using a cigarette lighter plug) and put a simple toggle switch on the box to kill the major draw when it's not being used.

Answer 4

Just a switching diode should work. Let's see, something like a N2001 ? Or you could just put a switch on the battery and turn the switch on just before you unplug the radio. Also consider putting in a in-line fuse. How about a capacitor to hold the voltage while you unplug the power and then throw the switch?

Answer 5

to much trouble if it's a modern truck use the lighter acc. if not go tothe fuse block and connect hotwire to bannana plug so it remains hot all the time, the amperage is small it won't hurt the truck, but if it's just because they won't let you hoook them up just get a 12 volt dry lantern battery and mount it in the glove box and hook it to the hot and ground of the plug, it will stay on when the power is off and you will have memory if it's running and has a 12 volt ALt. then it will charge it when running, it will also act as a ground plane for beter reception.

Answer 6

I'm a trucker too> buy your own truck!! Seriously, if your "company truck" has the fuses inside the cab, its a simple matter to find an "always hot" fuse in the fuse box, and run a wire from it to your radio. Todays radios don't draw enough juice to run the battery down, even over a weekend, so you'd only have to disconnect it when you change trucks.