power from motorcycle
dizave
Posts: 4
Happy holidays everyone.
I've build a PWM circuit for controlling some heated clothing I wear on the motorcycle when it is cold outside. It's running on my nice regulated power supply right now, which is great, but soon it will be in the real world, i.e. connected directly to the 12V battery of a horizontally opposed 1150cc vibrator.
My question is, what do I need to do to ensure the power to the PWM circuit is not going to fry anything? What kind of stuff goes on at the terminals to my motorcycle's battery that doesn't go on at my workbench, and how can I protect against it? The PWM is just some 555/556 stuff and some transistors.
I'm good with digital but this analog stuff is not my forte.
Thanks,
dave
I've build a PWM circuit for controlling some heated clothing I wear on the motorcycle when it is cold outside. It's running on my nice regulated power supply right now, which is great, but soon it will be in the real world, i.e. connected directly to the 12V battery of a horizontally opposed 1150cc vibrator.
My question is, what do I need to do to ensure the power to the PWM circuit is not going to fry anything? What kind of stuff goes on at the terminals to my motorcycle's battery that doesn't go on at my workbench, and how can I protect against it? The PWM is just some 555/556 stuff and some transistors.
I'm good with digital but this analog stuff is not my forte.
Thanks,
dave
Comments
You might get away with some simple filtering. That is a capacitors mounted from B+ to ground AT your 555.
You might also need to make a low pass filter, such as a small resistor in series then a cap to ground just before your 555.
Without knowing the frequency of the noise at the battery as viewed on a scope, hard to say what values.
For a start, maybe 50~100 ohms and 0.1 uF or less to ground.
batt
resistor
555
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Whenever you shut off the lights or honk the horn, big spikes travel throughout the system.
While many people seem to think of this as an easy kind of first project, it takes a bit of power supply study to get it right.
I myself have avoided automotive applications, but I would look for whatever they do to provide power to a good car radio and sound system for an optimal filtering system. There may be a pre-packaged chip out there for you.
While a 555 can very easily general a PWM from a variable voltage input - you might consider running the whole thing a a separate battery and use an optoisolator for connecting the output to whatever the power circuit is. The power circuit would be using the 12volt from the motorcycle. This would get you up and running while you were looking for the ideal filtering / power regulation.
In this way, you would never fry the 555 or if you later choose to use a BasicStamp in a more sophisticate application, you would never fry that either.
Of course the drawback is that you have that pesky second power supply battery to maintain.
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G. Herzog in Taiwan
They use big 1F caps or something.· HUGE cans! (no pun)
They use these to filter out the alternator and other motor noises.
You'd need some sort of constant current/voltage source that you could tap in to the cars 12V system.
Remember, too, that the car battery acts as a noise filter, although not the greatest.· Depending on what you have in mind, so far as devices added and when they'd run, and what type of vehicle, I'd add a 2nd battery that would run independantly.· You could also rig a circuit to monitor the voltage and switch it over to the main feed in order to get it to charge (babysteps first though!).
If you drive a Jeep or other truck, then you would have room for another deepcycle battery, but other vehicles seem to get very cramped in todays' engine compartments!
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Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
A "large" value electrolytic and a "small" value mica, ceramic or other.
The "large" value guy is for short term current supply, just like Robert said for the car stereo, and the small guy is for filtering "high" frequency noise.
Ken
Automobiles are going to convert to a high voltage system (32 volts I believe) in order to better address the problem in the age of solid-state electronics in the very near future.
The supply is particularlly limited on a motorcycle due to the size of the battery, wire size, and the power output available for an alternator. Also, the designer may have never considered laws requiring 24 hour operation of lights (especially in older bikes - like knucleheads).
Many motorcyclist hate having to run their headlights during the daytime (as required by state law) because the battery never really recharges. Many of them have to put their bikes on a battery charger every night before bedtime so that the battery will stay up.
As I mentioned above - a small micropower, separate supply for the logic with optoisolaton may be the best solution and it is a good place to start when going for a test run.
I suppose you could put a second alternator or a generator with second battery on a motorcycle just for goodies. It would be optimal - complete isolation.
ONE LAST AFTER THOUGHT.· WHY NOT USE A FAN AND PUMP HEAT FROM THE ENGINE rather than convert electricity to heat?· Your power consumption will go way down and you can still use the pulse width modulator to control the fan motor.· I suspect you will find yourself a lot warmer this way.
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G. Herzog in Taiwan
Post Edited (Kramer) : 12/26/2004 2:33:21 PM GMT