Help; 12 volt to 6 volt?

[piguglyshandydrinker]

I looking to get a reliable 6 to 7 volt (switched) supply from the bike to power a small 2 way radio on each of our bikes, using batteries is becoming a pain - can it easily be done with a resistor or something?
Preferably small & keep it simple - I'm no leccy expert!

At worst we could use a suitable mobile phone charger but would prefer something a bit smaller & without relying on ciggy lighter sockets.

Cheers, Phil

[Lutin]

There's a very simple device called a voltage regulator that would do what you want Phil. It would be able to provide you with a stable DC supply from the bikes nominal 12 volt system.

The principle can be found here -

HowStuffWorks "How Electronic Gates Work"

If you want, I can knock you up a circuit diagram, list of parts etc. Shouldn't take too long.

[Yeti]

Maplins! go and ask the nerd behind the leccy counter!

I've got a switchable cig charger unit, and am sure you could get something similar and take the guts out of it and wire it into something. It might need a heat sink or air flow though as it is vented?

[Lutin]

Before I start drawing up a list of parts (from Maplin's, if nowhere else) -

Do you need 6 volts, 7 volts, or just somewhere in between?

What is the current taken by the radios?

And, more importantly, how are you with a soldering iron an wee leccy components?

[Lutin]

Okay, here we go. This is the terribly complicated circuit that you will need -



And here is the pinout of the voltage regulator -



The Maplin part numbers are -

Voltage regulator - AW69A (TS7806CZ)

Capacitor C1 - RA52G

Capacitor C2 - RA49D

Oh, you'll also need a small bit of stripboard (veroboard) to make the circuit up on, but Maplin's sell this as well.

You might want to put a fuse in the supply from the bike's battery - something along the lines of twice or three times what the radio takes should be adequate.

These voltage regulators are pretty hard devices to destroy as they will cope with short circuits across their outputs and also being connected the wrong way round on the inputs too.

Any other questions, just ask.


Forgot to say, these regulators will supply up to 1 Amp, which I hope will be enough. You can (or rather should) bolt the regulators to some metal work for heatsinking. The tab is internally connected to the Ground pin.

[piguglyshandydrinker]

Okay, here we go. This is the terribly complicated circuit that you will need -



And here is the pinout of the voltage regulator -



The Maplin part numbers are -

Voltage regulator - AW69A (TS7806CZ)

Capacitor C1 - RA52G

Capacitor C2 - RA49D

Oh, you'll also need a small bit of stripboard (veroboard) to make the circuit up on, but Maplin's sell this as well.

You might want to put a fuse in the supply from the bike's battery - something along the lines of twice or three times what the radio takes should be adequate.

These voltage regulators are pretty hard devices to destroy as they will cope with short circuits across their outputs and also being connected the wrong way round on the inputs too.

Any other questions, just ask.


Forgot to say, these regulators will supply up to 1 Amp, which I hope will be enough. You can (or rather should) bolt the regulators to some metal work for heatsinking. The tab is internally connected to the Ground pin.

Thank you for the info, it's great & straight forward enough - even for a numpty like me to follow

The radio's use 4 AA batteries, so anywhere between 6 & 7 volts will be fine & I can't see them using that much power, but they seem to start playing funny bu**ers when the voltage drops below 5.6v (1.4v/battery)

Although it looks simple enough, I kind of feel that by the time I have fashioned it all onto some boarding, along with the inevitable rats nest of wiring & multitude of dodgy joints, a bo**ocking 'cos I have dribbler solder all over the kitchen worktops (AGAIN), then trying to weather proof it, a mobile phone charger might be a sensible option, already sealed (kind of) & with a small male plug already fitted at the other end.

I suppose I was hoping for "fit a xxx resistor on the positive feed & it'll be near enough..." type of reply.

Thanks again & I'll let you know the result

Phil

[pale rider]

Hi Phil
Me and winxp had a similar problem when we were preparing for TLD1 we were trying to get radio's to work and we ended up getting a bunch of astuff from maplins to help power them

basically all we bought was a cigarette-type socket which wired direct onto the bikes battery and they also sold plug in voltage adaptors with selectable voltage levels and we ran the radio's off those

we had lots of prblems and gave up in the end but that was how we sorted the power supply problem out

derek..

[winxp-master]

Yeah our problems were more to do with the radios than powering them, i got mine powered in the end by doing this:

I bought an adapter from maplins for a tenner that has a cig lighter adapter built in and switchable voltage, i also bought a female cig lighter and some wire... total cost was no more than about 15 quid.

I ran a wire from my bikes power (done so my ignition switched it on rather than on all the time) to the female cig adapter then plugged the switchable voltage adapter into that (set to 6 volts) then i cut the end of the switch wire (it had a phone type conector on) so that i could wire that into the radio. I simply removed the back of the radio and attached (with leccy tape for a trial run but would advise solder) the positive to...the positive etc etc... fired the bike up and voila, power all the time.

One thing to note is that when my ignition was switched off i lost my presets so i would advise either direct from the battery to avoid this or some kind of system wheras you can use rechargeable batteries in it but that kind of tinkerypokery is beyond my knowledge.

Phil, i think i still have a radio with wires poking out of it if you want to try that, i could mail you it for a play about... just let me know

Craig.

[Lutin]

In true Blue Peter style, here's one I made earlier -



The rule is there to give you some idea of the size of it - the box is about 3 inches by 2.

The large resistor is just there as a test load and at the moment this little gizmo is providing 120 mA at 7 Volts. If you want to test it Phil I can shove it in the post to you.

[piguglyshandydrinker]

In true Blue Peter style, here's one I made earlier -



The rule is there to give you some idea of the size of it - the box is about 3 inches by 2.

The large resistor is just there as a test load and at the moment this little gizmo is providing 120 mA at 7 Volts. If you want to test it Phil I can shove it in the post to you.

That looks great

you have a pm.

Phil

ps And cheers for the offer Craig but I'll tinker with the radios that we have.