LM317 regualted power supply + brushless motor.
azmax100
Posts: 173
I bought a vr regulated power supply which using LM317. I can power a brush motor but can't do it with brushless.
Why?
I have a cordless drill which I have spoilt the charger and cant get replace here in my place. i thought I can use the regulator but it disappointed me.
Why?
I have a cordless drill which I have spoilt the charger and cant get replace here in my place. i thought I can use the regulator but it disappointed me.
Comments
Often you see R/C airplanes using brushless motors with batteries, but they have a special converter between the motor and the battery.
Is your cordless drill a brushless motor or are you asking a second question?
If you want to build another charger for the cordless drill's batteries, you would have to provide more details about the batteries and the charger. What is the battery pack's voltage? What is its amp-hour rating? What kind of batteries are they [noparse][[/noparse]cadium, lithium, ?]?
In general the 317 will work, but provide a maximum of 1 amp charge. If that is too slow, there are ways to get more. If the battery is really dead, the 317 might shut down because the battery tries to draw over 1 amp. This is a safety feature.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
My cordless drill is brushless motor. the charger has spoilt.
I try using the power regulater by putting 2000uF 25V capacitor and put a diode on the positive supply, the drill run about a few second then the speed become slower than not turning. After a while I can use it back for few second. I have no idea what actualy happend as I have very little experience in electronic. As the problem arise I might learn something.
I try to charge the battery using the regulator (1amp) and it's successfully done.
Thanks.
Post Edited (azmax100) : 8/26/2008 6:16:19 PM GMT
Batteries are a topic that is very worthwhile. Charging usually requires limiting the rate of charge to a fraction of the total amp output of the battery. One-tenth is reasonable for lead acid, but one-thirieth is better for Nicads. Lithium batteries often start with a very low trickle charge and then ramp up to a faster charging rate in order to prevent fires. So you begin to see the chemistry of the battery decides much about the rate of charge and safety issues.
In general, all batteries prefer to be kept with a full charge when not in use. This state assures that they store longer and recharge more easily. If the battery is discharged below 50%, it generally suffers some premature aging and doesn't fully recover by recharging. This is more true of lithium than other chemistry.
So, the 1 amp regulated charge may be a bit quick for you electric drill. Battery manufacturers of course love quick recharges as they shorten the battery life and make you buy more replacement batteries. I would consider putting a temperature sensor on the battery and have charging turn off whenever you get above 45 degree centigrade [noparse][[/noparse]maybe lower]. The reasoning is quite simple, most overcharging creates excess heat which does the majority of the damage. Some of it is pressure that bursts the battery case and some of it is excessive by-products shorting out the battery.
"The Art of Electronics" has a good chapter on batteries. It doesn't tell all, but it is quite helpful. I find that the battery manufacturers really don't want us to know how to best maintain our batteries as they simply want to sell more. And these days, they want you to buy a specialized costly charger. With a little bit of common sense, one should be able to DIY a good charger. Having a thermal shut-down is the key to safety issues. Having controlled rates of charge will let you lengthen the life of a lot of batteries.
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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).
Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan