Powering things from bikes...

[Craggles]

Hi,

My MP3 player has a crap battery life. This means its useless, because I have to keep stopping to change the battery. So I thought, "I know, I'll power it from the bike!".

Can anyone see a problem with this circuit? (The MP3 player would go where the voltmeter is)... The player runs on a 1.5v AAA battery... I took the resistor values from one of the 2.99 Maplin packs.

Cheers, ,

Craig
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[Azmodeus]

Hmmm, dont know much about electrics (other than finger+socket=pain). So the only advice I can give is be careful

It may be easier to do a similar circuit, but instead of putting it on a bike battery, use one of those square 12v batterys.

Just a thought

[TheShaggyDA]

Values look ok, but you might want to put some smoothing in there, maybe a regulator.
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[i:6e3bfc7581]But still I fear and still I dare not laugh at the madman...[/i:6e3bfc7581]

[Kram]

a bike battery, when running isn't really 12v, it's 14.4v (well should be) so you should be very carefull. also try putting a fuse in there too. i'll have a think over a circuit like this, and get back to you.
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[TheShaggyDA]

You might want to look at something like this :-

https://www.aaroncake.net/circuits/cdsupply.htm

You could use the 5v version, and then use resistors to drop it to 1.5 volts.
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Current: CB500 Previous: CB100N, CB250RS, XJ900F, GT550, GPZ750R/1000RX, AJS M16, R100RT, Enfield Bullet

[i:6e3bfc7581]But still I fear and still I dare not laugh at the madman...[/i:6e3bfc7581]

[nick.h]

i thought AAA battery life in the mp3 player is 8 hours?
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[mr.z]

Find a car adapter for your mp3 player (or somethuing outputing the same power) take the adapter appart, wire the inside pin to your + (allways on rear lights are a good one, you just need your lights on all the time) and outside to -/ground point. Alternatively drill small holes into the side and center pin and feed the wire in, then solder, tape it up good and propper.

Fit a fuse (1amp or less) closest to the + source as possible.

Idealy you should run this off a relay, shouldn't be a problem though...

Use ONLY the right wires suitably thick, use only the right connectors, solder them, use heat shrink, never let the + touch the frame.

Be ery very carefull, at best you could knacker your bike, at worst you could go up in flames while pootleing allong down the road. If you haven't got the right equipment or are unsure then leave it allone!*


/*personal experiance
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[pipnet11]

Take the potential divider to 5V then get a voltage regulator to 1.5V (I think they were 78015. 5V being 7805, 12V 7812 etc) This means that when the voltages are changing from the divider as the battery is charged or drained there will always only be 1.5V at the player. This is important as you could have the voltage at the player changing from 1V to nearly 3!! the regulator will keep it constant with an input voltage of about 3V to 10V.

Problem: 1.5V regulators are a sod to get. Maplin and RS electronics only list down to 78033 (3.3V) howevver these work with an input up to 20V so you could put the divider after the regulator if you wanted.

Hope this didnt cause more questions than answers
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[pipnet11]

Just noticed TheShaggyDA's circuits, that looks like what i was on about, just put the resistors after that and work out the values to be 1.5V (I would do it for you but im lazy)
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[True Blue]

Is there an adapter available that lets you plug the MP3 player into a car cigarette lighter? If there is, buy that and use the circuit in that. HTH
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[True Blue]

Something like this Maybe? You could hard wire it to your battery via an inline fuse.
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[Craggles]

If I wired in (a suitable circuit, with a regulator - or a modified car adaptor) after the fuse for the electrics on the bike, would that suffice as a fuse... or should I do it seperately?

I'm liking the idea of taking apart a Car Audio kit, rather than building something from scratch.... I've possibly demonstrated the limit of my electronics knowledge in the post above!

How do regulators work, and how hot do they get - the site mentioned the need for a heatsink, does this need to be placed somewhere within a windblast... or could it double up as a heating element for my jacket? I've just looked on RS and Maplin and have no idea what I'm after on that front... perhaps I'll go down the premade route

Craig
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[palmer]

backpack + portable power pack = sorted.

[True Blue]

Premade route is definately the easiest IMO. I would give it its own fuse. To hook it up without opening the thing you could always get a cigarette lighter socket thingy like this one...

https://www.vehicle-wiring-products.co.uk/VWPweb2000/photos2/042248.jpg

I would cut the clamps off and put on ring crimps though
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[Fortuna]

Always work out on the highest voltage that will be applied. In a bikes case it would be 14.4 approx.
That voltage divider has a very low max current output. It comes out at .007 amps or just 7 milli amps. Bearing in mind a standarf LED uses 25-30 ma I'd say an MP3 player uses more (correct me if I'm wrong of course).
If you want to "DIY" I'd use something like an L200 or LM317 regulator as they shut off if they get too hot or too much current. You can make them variable voltage too which is great if you want to swap it for something else later.
I could knock a circuit up in 2 seconds, and could even build you one if you like or if you are learning let you build it yourself.

[Fortuna]

[stryker]

Yep, you will need regulation of the current as said above, while the battery does a fair job of stabilising the voltage, it will vary.

I'd get a ciggy lighter fitted then buy an adaptor that allows you to pick a voltage.

OR, if you really want to do it the hard way, look into PVMs (pulse width modulation). Its a pretty good way of regulating voltage, but some what more complex. The plans are on the net.
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Now what?

[Demonic69]

And Inverter can work well when the bike's running, but the battery and charging circuit need to be in good nick.
I've fitted as cig adapter to my bike and run a laptop, airbed pump, lights and a few other things off it with no problem. I would suggest a generic charger/adapter with selectable voltage for the MP3 player though.
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[Grubby]

Just buy a Goldwing, they come with a radio attached.

[pipnet11]

[Milo]

Why not get an MP3 player which has a rechargeable battery?
If I was paying money for one i'd make sure it doesn't take normal battery's.
My MuVo2 lasts 8+ hours and stores 4gb - and you can get 'em for around £130 now I think.Not the solution you're after but it's a much simpler one.
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