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nick76
Starting Member
United Kingdom
7 Posts |
Posted - 21/08/2007 : 14:48:51
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Hi all,
I'm really sorry if this is a basic (dumb) question but...
Can anyone tell me (not that tech savvy) what a Permanent Magnet Motor is? And how to tell it apart from other motors?
Many thanks
Nick
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ll81
Junior Member
124 Posts |
Posted - 21/08/2007 : 16:58:06
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Rather than use a field winding to generate a secondary magnetic field it is done by magnets. They need to be bigger than other types of motor for a given output but consume less power. Best used on DC motors that require speed controll.
woo-hoo |
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Peter Williams
New Member
United Kingdom
51 Posts |
Posted - 30/08/2007 : 20:11:05
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Is there a maximum rpm that a savonius wind generator will turn at?
Since batteries are self regulating could I charge a 6v battery with a 12v solar panel? |
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gotwind
Forum Admin
United Kingdom
765 Posts |
Posted - 30/08/2007 : 20:22:03
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1st question.
A savonius (or vertical axis wind generator) can only spin at the speed of the wind it 'see's'. It can't spin any faster.
This has some advantages, it will never over speed and is somewhat safer, also it doesn't need facing into the wind like the standard Horizontal setups - efficiency is considerably less unfortunatly with vawts.
Second question, I will pass to someone else please - personally I don't see why not....
The Futures Green - Getwind of it. |
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BushWhacker
Junior Member
Canada
255 Posts |
Posted - 31/08/2007 : 03:20:35
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Peter, re: Since batteries are self regulating could I charge a 6v battery with a 12v solar panel?
From what I have read, (and that's a whole bunch) the receiving battery will suck up the juice (more voltage than it's own rated voltage) until it is fully charged. When the battery (or battery bank) is fully charged, (in your case almost 7 volts measured while charging) if you keep charging it, it will become a DANGER ZONE! if the amperage is high enough. Over charging will also reduce the life of a battery at anything over about 2 amps. That's why battery chargers are usually regulated.
Cheers!
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein |
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Del
Junior Member
United Kingdom
362 Posts |
Posted - 31/08/2007 : 09:13:51
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Hi Peter,
Some advice I've read recently from a battery charger co. is that the battery voltage should not exceed 13.8 volts for long periodsand 14.4 volts for short periods (8 hours maximum).
Cheers
Del. |
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ll81
Junior Member
124 Posts |
Posted - 31/08/2007 : 16:21:41
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It will suck up the current until it is charged, after that point you will want a circuit that disconnects the panel. I have never done any research on solar panels but can't imagine running it in such overload conditions is favourable.
woo-hoo |
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Peter Williams
New Member
United Kingdom
51 Posts |
Posted - 05/09/2007 : 21:48:51
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I'm unfamiliar with stepper motors, which devices are the best to get them from and what sort of information/stats should I be looking for when sourcing a motor?
Also what sort of power are we talking about with them? |
Edited by - Peter Williams on 05/09/2007 21:49:17 |
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gotwind
Forum Admin
United Kingdom
765 Posts |
Posted - 06/09/2007 : 16:53:59
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Hi Peter.
I think steppers are used in robots and the like, anything that needs accurate micro rotations.
Theres a few on eBay - I didn't have much luck with one, getting only 4 watts of power.
More info on this page
http://www.gotwind.org/stepper_motor.htm
Ben
The Futures Green - Getwind of it. |
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Peter Williams
New Member
United Kingdom
51 Posts |
Posted - 11/09/2007 : 17:09:43
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| I have some ultrabright 10mm leds that run on a forward voltage of 3.6v. Is it ok to use 3 rechargeable batteries (1.2v each) or is there a chance of blowing the lights. I would like to charge these batteries in situ connected to the leds. |
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ll81
Junior Member
124 Posts |
Posted - 12/09/2007 : 22:55:42
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You would do alot better to use four and a series resistor.
Cheers, Liam
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Peter Williams
New Member
United Kingdom
51 Posts |
Posted - 17/09/2007 : 15:58:49
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A-ha Liam!
Whats a series resistor and how do you know what type to use?
4 batteries would be 4.8v through a 3.6v led, could you please explain.
thanks
Peter |
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ll81
Junior Member
124 Posts |
Posted - 18/09/2007 : 20:30:54
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LEDs Vf (forward voltage max) is the maximum voltage drop that has been measured during batch test of the components. Unlike a bulb the voltage will be high enough to cause current to flow or not. Once that forward voltage is reached the load impedance on the voltage source is low, if the voltage is high the current will be high, possibly to high and no more LED. If it is low the LED won't light. The actual voltage of the batteries will vary and the exact Vf of the LED.
By using more voltage than needed you can guarantee there will always be enough to light the LED and use a resistor in sereies in the circuit to limit the current. 4.8v max - 3.6v = 1.2v. If If max (forward current) is 20 ma then 1.2/0.02=60 (V/E=R). Put a 60 ohm resistor in series with the battereis-LED to prevent destruction and ensure the LED stays on as the battery voltage falls.
Cheers, Liam
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BushWhacker
Junior Member
Canada
255 Posts |
 Posted - 20/09/2007 : 20:11:28
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After Ghurd's great write up concerning Electricity and Charging on Del's Solar Panel string I am still left with a couple of questions.
The leads coming from a hub I will be using are 14Ga. Are there any gains to be had by running heavier wire (12Ga. 10Ga.?) from the 14Ga. leads to a battery on a short run, say 15Ft? What if you have a longer run say 50 Ft?
I realize that the 14Ga. leads will act as a "choke point" of higher resistance in this set up but just do not know if lower resistance down line would help deliver more power to the battery.
Thanks for helping the electrically challenged.
Cheers!
BW
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein |
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Peter Williams
New Member
United Kingdom
51 Posts |
Posted - 11/10/2007 : 19:30:42
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I want to make a small light from 10 leds in parallel. I am using a 4.8v (4 x 1.2 rechargeable batteries) and know that I need a 60 ohm resistor (thanks Liam).
Do I use one resistor in the circuit or one per led. I was also under the impression that the resistor is connected to the positive side of the led?
The idea I'm aiming at is something similar to this
http://www.instructables.com/id/Low-Profile-LED-Shelf-Lighting/
but from 4 1.2v batteries
Peter |
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FAQ page - help please
