trying to regulate dc voltage

[michael ritchie]

I installed a older radio on a motorcycle. My alt at idle holds at 10 to11.5 volts problem is when running at a higher rpm the voltage runs from 13.5 to 14.3 and the radio shuts on and off what can i put in line to keep the voltage under 12 volts max

 

[GreenGiant]

I installed a older radio on a motorcycle. My alt at idle holds at 10 to11.5 volts problem is when running at a higher rpm the voltage runs from 13.5 to 14.3 and the radio shuts on and off what can i put in line to keep the voltage under 12 volts max

You can put a 12 volt regulator (7812 for example) in line with the radio, just make sure that you have a cut off for when the bike is off

with the 7812 it will output 12 volts so long as the input is above 2volts 1amp and below 35 volts

 

[michael ritchie]

i need to keep it at 5amp min

 

[davenn]

i need to keep it at 5amp min

Do you mean the old type radio draws 5Amps?

On well the 7812is no good for 2 reasons
1) there isn't the headroom voltage to run the regulator. ( that's the primary problem)
2) the 7812 can't supply 5 Amps anyway without additional circuitry for current pass

What sort of radio is it? Is it one that was originally designed to run in a vehicle?
If so then the extra volt or two isn't going to be a problem any way.
What is the actual designed operating voltage of the radio anyway... You haven't specified that

Dave

 

[michael ritchie]

its a older radio made by clarion and sold as a harley davision radio that mounts to the handle bars with two speakers. I think its about 40 wat speakers and just quessing at the 5 amps. the radio works great as long as the voltage stays under 12 volts when it peeks out at 14. it overloads the radio and it shuts down and than right back on every three seconds this radio is no longer made but i like it so ill do what ever it takes to keep it
mike

 

[davenn]

Ok
This would suit a DC to DC voltage converter so that with a varying input voltage...10 to 14 V, it would still produce a 12 V output. And handling 3 to 5 Amps would be easy to do

I don't know a specific model offhand would have to go searching and am sure you are capable of that they are quite small modules less than the size of a cigarette packet

Dave

 

[duke37]

You could try putting a silicon diode in series with the supply to the radio, this will drop a volt or so. Chose a 5A diode.

There is no explanation of why the radio is so fussy, perhaps you have not peeked at the peaks!

 

[davenn]

You could try putting a silicon diode in series with the supply to the radio, this will drop a volt or so. Chose a 5A diode.

There is no explanation of why the radio is so fussy, perhaps you have not peeked at the peaks!

Well.... Around 0.7V drop per diode

But your second content is one that I have also pondered. Any radio designed for a vehicle should be capable of handling several Volts of swing. If it can't it would almost infer a prob with the radio.

Putting 2 or 3 diodes in series will drop that higher voltage ok but it's also going to drop the lower idle voltage down to around 9 V. Wonder if the radio will still work at 8.5 to 9 V ??

Can only but experiment and see what happens
Choose hi current diodes as duke37 suggested

Dave

 

[gorgon]

Are you sure that this radio is made for 12V, and not made for a 6V motorcycle system? If it works at 6-7V you could just use a small DC-DC switcher to convert down to this voltage.

TOK

 

[cjdelphi]

You may need a step up / down regulator... only because of the fact when you idle it hits 11volts, with a regulator there's going to be a certain voltage (depends on which regulator) where by it will drop out, eg, if wanted to power a 12v modem and i stick a 12v regulator from a 14.5v supply no problem but when it hits say 12v you'll see a voltage drop which can be around 10volts even though the battery is supplying 12.5volts.

in which case you need a buck/boost circuit.

if it runs on say 10/11 volts you might be able to get away with a step down switching regulator (as the dropout is lower than a linear regulator such as the lm317)

check out these....

http://stores.ebay.com.au/Marcmart-...&_sticky=1&_trksid=p4634.c0.m14&_sop=15&_sc=1

I've bought 4 regulators from him, step down and step up, they're really quite well built (except the cheap ones under 5 bucks) I get 2 amps with not too much heat. i've spent 3x as much building one as a kit.....