Help! I know nothing about electronics!

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timothyscott
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Help! I know nothing about electronics!

Post by timothyscott » Tue May 25, 2004 1:03 am

Ok, here is the deal, I know close to NOTHING about electronics and if anyone can help I would greatly appreciate it. I am "helping" my son put together a project. The project consists of an engine that will require 3v to fire it. the engine drives the vehicle and a 9v motor. The 9v motor is used as a generator or alternator. If the generator would make (not sure it would) 9v of electricity, is it possible to use 3v to run the engine and the extra to recharge the battery. And is there any device that could be used to store any left over energy? The goal is to have a system that wouldn't even need the battery in the first place to start it, it would have energy stored up in "whatever" for the initial start up later. If this is a really dumb question and we're trying to reinvent the wheel just let me know. Thanks for any help.

Mike
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Re: Help! I know nothing about electronics!

Post by Mike » Tue May 25, 2004 5:01 am

So are you saying that you want to have one motor produce power and move the vehicle and also allow another motor to produce even more power than that to make it never stop moving?<p>if so, it isnt possible.<p>or, if you are saying you want to make a mini-car that uses a real gas engine with electric start hen a 9V motor to charge the battery, then yes, you can do that.<p>you will need a 3V rechargeable batteries (3 AA rechargeable NiCd in a row would work, even though it would give 3.6V). You connect the positive of the 9V motor to the + of the battery set and the same with the negative. Then wire the same motor to the 3V fire motor but put a push button switch in line with the + wire.<p>After a while, the rechargeable batteries will charge and will stay charged.<p>If you need a picture showing where to connect everything, i can help you with that.

bridgen
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Re: Help! I know nothing about electronics!

Post by bridgen » Tue May 25, 2004 5:02 am

In order to give a (more) complete answer it would help if you explained exactly what sort of "engine" it is. <p>You can certainly use the motor as a generator but if it is a d.c. one then it will not function as an alternator (which is produces a.c.) but will function as a dynamo (which produces d.c.)

Mike
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Re: Help! I know nothing about electronics!

Post by Mike » Tue May 25, 2004 5:05 am

David, actually i believe it is the other way, a dynamo is AC and an alternator is DC.

bridgen
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Re: Help! I know nothing about electronics!

Post by bridgen » Tue May 25, 2004 5:35 am

No Mike.

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dacflyer
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Re: Help! I know nothing about electronics!

Post by dacflyer » Tue May 25, 2004 11:42 am

i been working on gas engines since i was 12 and i never heard of a 3 volt starter.....

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MrAl
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Re: Help! I know nothing about electronics!

Post by MrAl » Tue May 25, 2004 11:56 am

Hello there,<p>The answer depends on what you are really trying
to do, which wasnt that clear from your original
question...<p>
If you are saying that you have a 'gas' engine
that 'starts' using a 3v battery then you can
use the 9v generator to charge a 3v rechargeable
battery so you never need an external battery
to start the gas engine.<p>
If you are instead saying that you have a 3v motor
that 'runs' on a 3v battery and also runs a 9v
generator and you wish to charge the 3v battery
from the 9v generator then it wont work for
very long due to conservation of energy.
Eventually (probably not that long) the
system will run out of energy and stop.<p>
Take care,
Al
LEDs vs Bulbs, LEDs are winning.

timothyscott
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Re: Help! I know nothing about electronics!

Post by timothyscott » Tue May 25, 2004 12:43 pm

thanks for all your help. No, It is a gas engine. I guess after thinking more about it we're trying to devise an electrical system for a rc car about the same as in a regular auto. I think its possible I just don't have the know how to do it.

josmith
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Re: Help! I know nothing about electronics!

Post by josmith » Tue May 25, 2004 1:19 pm

It's not so far fetched if you think of a lawnmower charging system rather than an automotive one. In small motors they use a magnet imbedded in the flywheel and a coil in close proximity to the motion. One diode is all you need for between the coil and the battery.

timothyscott
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Re: Help! I know nothing about electronics!

Post by timothyscott » Tue May 25, 2004 5:13 pm

ok, so now how would i set this up?

josmith
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Re: Help! I know nothing about electronics!

Post by josmith » Tue May 25, 2004 5:52 pm

Looking back at your question I see that you already have a dc motor driven as a generator. This may be a better idea than trying to create your own by adding a magnet to a rotating part of the car and winding a coil to generate electricity.<p>Either way use a diode between the generator and your battery so that it won't discharge through the generator while the motor is stopped.<p>Your question also begs for something other than a battery to store energy for the next restart. I don't believe there is anything else to use. Like your car you have to start with a charged battery and hope that the generator makes up the difference in charge for the next restart.<p>It's still unclear exactly what you mean about needing 3volts to "run the engine" Does it have a battery ingition?

timothyscott
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Re: Help! I know nothing about electronics!

Post by timothyscott » Tue May 25, 2004 6:19 pm

thanks, Yes it does have a battery ign. plus the car has light on it (flashing)and thats what the gen. is going to power.

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MrAl
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Re: Help! I know nothing about electronics!

Post by MrAl » Tue May 25, 2004 9:18 pm

Hello again,<p>I was going to suggest the same as josmith.
A single diode sounds good, type 1N4002 or
similar, but better is 1N5817 for your app.<p>With the motor running, measure the output
voltage of the 9v generator to determine which
lead is the positive (+) lead (usually the
RED lead of the meter is positive).
Connect the diode anode to the (+) lead of
the motor, cathode to the 3v battery (+) tab.
The negative (-) lead of the motor goes
to the negative (-) lead of the battery.
The battery is made from two NiCd batteries
in series (dont use non-rechargables).<p>In case you dont already know, the cathode
lead of the diode (which has two leads) is
the lead coming out of the end that is marked
with a 'band' of paint, usually white paint.
The other lead is the anode. This of course
means the 'band' end lead goes to the (+)
of the battery pack.<p>The connections have to be correct or the
batteries, motor, or diode could be destroyed.
If you have any questions about the connections
stop and ask first :-)<p>It is probably a good idea to charge the
NiCd's for the first time before you connect
them to the diode/motor.<p>Typical battery sizes would be AA or Sub-C,
but you may wish to try AAA's to reduce the
weight. NiMH cells wont be as good for your
app as NiCds, even though they hold more
charge.<p>You could measure the current out of the motor
and the current during engine startup
to get an idea how long the engine has to run
to be sure to get the batt's charged up fully
again after a typical start.<p>As a final note, it is possible to overcharge
the batteries if the generator puts out too
much current. To find out, you would have to
measure the current going into the batteries
while the engine runs. If it goes too high,
you may have to add a resistor in series.
The AAA's should only get about 20ma of current,
depending on how long a typical drive/flight is.
If the 9v motor is very small (like 1" long)
you may not have to worry about it :-)<p>The 9v motor will eat up some horsepower
while charging you know :-)<p>Good luck with it!<p>Take care,
Al
LEDs vs Bulbs, LEDs are winning.

dyarker
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Re: Help! I know nothing about electronics!

Post by dyarker » Tue May 25, 2004 10:24 pm

RC car? 3V to start?<p>Sounds like a glo-plug engine. To start, 3V is connected to the glo-plug, a small coil in the cylinder gets hot, turn the engine til it catches. Then the 3V can be removed because each ignition stroke keeps the coil hot enough to ignite the air/fuel at the top of the next compression stroke. Fuel is alcohol and oil, or Nitro-methanol oil.<p>Is this the beast we're talking about?<p>You need a resistor and a diode to recharge the battery. As mentioned, the diode prevents discharging the battery thru the generator when not running. The resistor limits charging current so you don't burn up the battery. Normal NiCads need like 16 hours for a full recharge. I don't think your gas tank is that large :D Use "high rate" NiCads. (The battery packs for electric RC cars are "high rate".)<p>Is there a 6V to 7.2V battery pack for the receiver and servos? It may be possible to get 3V for starting from it by going thru a zener diode. Depends on how much current a glo plug uses and size of the pack.<p>How big (in terms of electrical power) is the 9V motor? Will it generate enough current to recharge the battery in reasonable time and run the lights? For that matter what kind of lights and how many?<p>For weight and volume to energy storage capacity ratio it is hard to beat batteries.<p>------------------------------------------<p>If the engine is like a mini-chain saw engine with a spark plug, then I don't understand where the 3V comes in. But what I've said applies anyway.<p>------------------------------------------
added - I was still typing when MrAl posted, and I agree.<p>C U L -<p>[ May 25, 2004: Message edited by: Dale Y ]<p>[ May 25, 2004: Message edited by: Dale Y ]</p>
Dale Y

timothyscott
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Re: Help! I know nothing about electronics!

Post by timothyscott » Tue May 25, 2004 11:04 pm

thanks for all your help. Im not to sure of the engine. He built it in shop class as final project. It has 2 clyn. (small) and uses a charge to arc(?) and fire the engine. Totally just a toy now. Its going into a tow truck chassy and thats where the lights come in (flashers on top) eventually (this will be another problem) we want to use a small electro magnet on the "crane" to pick things up. I know all this is confusing and I appologize but like I said in the beginning Im pretty much lost when it comes to Electronics and the guys at radio shack knew about twice as less as I do. But you all have helped out tons thanks alot.

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