Hi Guys, I wonder if anyone can help.
The plan is to fit a modern radio in an old positive earth car. I know one option is to convert to negative ground - actually that has already been done but firstly the time clock does not work and I'm stuck with it as it is part of ther rev counter, and secondly I would like to keep the car as original as possible so I plan to convert it back to positive earth.
Regarding the radio the most obvious choice may be to isolate the car radio from the car body but I'm not entirely happy with that as it is too vulnerable to the occasional short and possible fire. I know fuses can protect things but I'm still not happy with that idea! The other option I gleaned from the internet may be to use a voltage doubler/multiplier, connect the input positive to the vehicle ground, and take the output between the vehicle ground, (+12v) and the output positive (+24v). In theory I guess this would work but I don't know what type of circuit to use. Also the output would have to be fairly consistent between 12 and 14 volts.
I've come across many dc voltage doubler circuits but most of them use 555 timers or similar devices that I don't think will handle the current requirements. I also suspect the problem with some circuits would be that if the 24v output is well regulated, the voltage as described above would drop as the vehicle charging system starts to work. Unless anyone can tell me otherwise it seems that the only option may be to use an inverter to convert the dc to ac, a transformer to boost the voltage, and then a rectifier to convert back to dc with some kind of voltage regulation. In this setup would it be possible to earth the positive input and the output negative together? I think that the use of a transformer will isolate the two so there would be no problem doing this. Can anyone confirm?
Or does anyone have any other ideas?
The present radio in the car (as someone has previously converted it to negative earth to fit this - as I said before I plan to convert it back) has an input fuse rated at 10 amps so this circuit must be able to deliver that as a minimum. This won't be the actual radio going in (this one doesn't work - another project for another day!) but I guess it will be something similar.
Over to you guys!...
The plan is to fit a modern radio in an old positive earth car. I know one option is to convert to negative ground - actually that has already been done but firstly the time clock does not work and I'm stuck with it as it is part of ther rev counter, and secondly I would like to keep the car as original as possible so I plan to convert it back to positive earth.
Regarding the radio the most obvious choice may be to isolate the car radio from the car body but I'm not entirely happy with that as it is too vulnerable to the occasional short and possible fire. I know fuses can protect things but I'm still not happy with that idea! The other option I gleaned from the internet may be to use a voltage doubler/multiplier, connect the input positive to the vehicle ground, and take the output between the vehicle ground, (+12v) and the output positive (+24v). In theory I guess this would work but I don't know what type of circuit to use. Also the output would have to be fairly consistent between 12 and 14 volts.
I've come across many dc voltage doubler circuits but most of them use 555 timers or similar devices that I don't think will handle the current requirements. I also suspect the problem with some circuits would be that if the 24v output is well regulated, the voltage as described above would drop as the vehicle charging system starts to work. Unless anyone can tell me otherwise it seems that the only option may be to use an inverter to convert the dc to ac, a transformer to boost the voltage, and then a rectifier to convert back to dc with some kind of voltage regulation. In this setup would it be possible to earth the positive input and the output negative together? I think that the use of a transformer will isolate the two so there would be no problem doing this. Can anyone confirm?
Or does anyone have any other ideas?
The present radio in the car (as someone has previously converted it to negative earth to fit this - as I said before I plan to convert it back) has an input fuse rated at 10 amps so this circuit must be able to deliver that as a minimum. This won't be the actual radio going in (this one doesn't work - another project for another day!) but I guess it will be something similar.
Over to you guys!...
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