Reducing DC motor speed w/min components



A really simple solution. But the battery pack is modular (encapsulated) and would require modification of the pack. Also, would result in imbalance of charge in the cells. And from what I understand about Li-Ion chemistry. they don't balance very happily during charge.
I think a 555 PWM solution is in my future.
Thanks,
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DaveC
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DaveC wrote:

A two pole c/o series/parallel (slide) switch... and the modification is usually pretty trivial. The slide switch can be very small and won't require anything like the space that an electronic unit (including its own switch/control) will need.
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Sue



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Thanks, Sue.
Modifying the battery does look like the obvious route. As does the series/parallel switch (what's "c/o"?). I'll have to find one to handle max current, of course, in such a small package...
The main objection I have to applying this mod is that it means I'll have to rely on my memory to place the switch in series before placing the pack in the charger. Charging two 3.6v lithium-ion cells in a 7.2v charger is Not A Good Thing (sm). I'll have to balance the pro's and con's. Unless you have an idea to help protect the cells & charger from that possibility... (c:
FYI, it's this tool: <http://www.makitauk.com/index.php?special=product_detail_popup&pid 64&catid >
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ISTM that the right solution here is a plug-on reduction gearbox. Doing it mechanically would also do the required increase in torque. If there is not one on the market already then someone is missing a commercial opportunity.
Say a 2.5 or 3:1 ratio, input/output shafts inline, make both shafts as hex sockets so that it can be used to increase or decrease speed. Supply a hex bar to couple the screwdriver/drill and gearbox hex sockets.
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Tony Williams.

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2000 rpm 7.2V cordless screwdriver? I don't beleive it.
Bye. Jasen
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jasen sez:

Actually 2300 rpm: <http://www.makitauk.com/index.php?special=product_detail_popup&pid 64&catid >
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DaveC
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That's an impact driver and I suspect that it needs the rpm to get the inertia to ride through the impacts. Its the impacts that torque the screw, not the direct motor speed/torque. Reducing the speed may not have the effect you desire.
Notice the next driver down, which is not an impact, and which does the nearly the same torque by means of a larger step down in the gearbox.
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Tony Williams.

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Thanks for your comments, Tony.

I want to double the use of this tool by providing lower speeds. Yes, the impact is useful for driving/undoing tight screws, but it's useless (way too fast) when, for example, installing small screws in covers on residential light switches or receptacles.
By providing low-torque low speeds, I make this tool useful for small screws, too. Yes, I could buy another tool to cover that purpose, but for a few bucks, (and having a bit of fun in process of design and implementation) I can do this.
(And I already own it...)
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