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screwgun triggers

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Michael Robinson

Jan 1, 1970
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I have a cordless impact driver and drill set I use all the time. How does
the speed control in the trigger work, is it just a rheostat? It's been a
long time since I took a drill apart, but I don't remember seeing any active
circuitry.
 
T

Tom Biasi

Jan 1, 1970
0
I have a cordless impact driver and drill set I use all the time. How does
the speed control in the trigger work, is it just a rheostat? It's been a
long time since I took a drill apart, but I don't remember seeing any active
circuitry.
I haven't taken one apart for a while but the last time I did it was a
little PWM circuit.

Tom
 
M

Michael Black

Jan 1, 1970
0
I have a cordless impact driver and drill set I use all the time. How does
the speed control in the trigger work, is it just a rheostat? It's been a
long time since I took a drill apart, but I don't remember seeing any active
circuitry.
I've always wondered. I bought my Black & Decker drill in 1975 and it has
variable speed (but doesnt' reverse). It's trigger is a very small
package, and I don't see anything elsewhere, but it can't be a rheostat,
too small for that too.

Michael
 
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Michael Black

Jan 1, 1970
0
SCR speed control, all in the trigger housing. I've had to replace
several in the last few decades, but I still have plenty of new spares.
I stocked up when the BD surplus store had them for 25 cents each. I
bought all 62 they had in stock. The first two I used to convert single
speed drills to variable paid for all of them. :)
I think that occurred to me at one point. I think I paid $25 Canadian for
this drill in 1975, and the only thing I've had to do to it was replace
the brushes about 20 years ago.

About five years back, I found another Black & Decker drill about the same
vintage (still a metal case) for $3 at a garage sale, bought it as backup.
And then found another one of the same vintage in the garbage when the
students moved out. One of the others at least has the reversing switch.
But now, I have one to leav in my drill press adapter.

Michael
 
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Michael Robinson

Jan 1, 1970
0
Michael A. Terrell said:
SCR speed control, all in the trigger housing. I've had to replace
several in the last few decades, but I still have plenty of new spares.
I stocked up when the BD surplus store had them for 25 cents each. I
bought all 62 they had in stock. The first two I used to convert single
speed drills to variable paid for all of them. :)

This is cordless (DC) equipment I'm inquiring about. I can see putting an
SCR in a drill that runs on AC. What circuit do _cordless_ drills or impact
drivers use?
 
P

Paul Conners

Jan 1, 1970
0
SCR speed control, all in the trigger housing. I've had to replace
several in the last few decades, but I still have plenty of new spares.
I stocked up when the BD surplus store had them for 25 cents each. I
bought all 62 they had in stock. The first two I used to convert single
speed drills to variable paid for all of them. :)

I did something similar with Milwaukee battery sockets (on the bottom of the
18V drills). I've epoxied these adapters in Bosch and other 18V drills & saws
that someone is throwing away. Now all take the M 18V battery pack.
 
E

ehsjr

Jan 1, 1970
0
This is cordless (DC) equipment I'm inquiring about. I can see putting an
SCR in a drill that runs on AC. What circuit do _cordless_ drills or impact
drivers use?

PWM, as Tom stated in the first reply.

Mike Terrell was replying to Mike Black about his 1975 B&D drill,
which is was not cordless. In Mike Terrell's reply to you, his
answer was PWM.

Ed
 
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Michael Black

Jan 1, 1970
0
A more recent B&D I took apart (a replacement battery cost more than a new
drill) had nothing more than a MOSFET and a slider pot linked to the trigger,
the heatsink was custom made (cast aluminium) to fit as much fins as possible
in the space behind the brushes.
That might be, though back in 1975, I don't recall power mosfets.

And while the variable speed isn't perfect, I think it's too smooth to be
a rheosstat (or a mosfet or transistor acting as a variable resistor).

Michael
 
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