Impuls fuction for cordless screwdriver power tools

[smilem]

Impuls DIY fuction for cordless screwdriver power tools

Hello, I have an idea to make the impuls function on a makita brand cordless screwdriver.
It is very handy to unscrew old bolts, or to drill to shiny surfaces like tiles.

Unfortunatelly the impuls is metabo "inovation" - if you can call pulsed power to the motor
inovation. It is available on few cordless drills, and I have one of them that's when I understool
how handy this is.

You can see a video here how the impuls function works
https://www.youtube.com/watch?v=86l4Ft_xAr0

Is is possible to design a simple circuit with power fet, etc to pulse the power to the motor?
I'm sure a power fet, capacitor to select pulse cycle lenght and some other parts would make this
doable for DIY project.

 

[alec_t]

Are you sure the Metabo drill (which is an impact drill) works by pulsing the motor? Most impact drills work by use of a mechanical pulser (a stepped ramp).

 

[tcmtech]

Making a normal cordless drill pulse like that would be rather easy.

Just use a 555 timer to switch the voltage lead (fixed + point) on the speed control potentiometer from its normal positive reference voltage down to ground and back at what ever frequency you want.

By doing that you will have pulse control over the entire speed range of the drill when the pulse circuit is on.

 

[alec_t]

Making a normal cordless drill pulse like that would be rather easy.

It would (unless the pulsing had an adverse interaction with the internal PWM); but the average power would be reduced, so any impulse effect is likely to be weak?

 

[tcmtech]

If you are just toggling the trigger potentiometers output from high to low the PWM circuit should just see that as if the trigger is being pulled and released fast.

 

[alec_t]

Yes, it should do.

 

[smilem]

Are you sure the Metabo drill (which is an impact drill) works by pulsing the motor? Most impact drills work by use of a mechanical pulser (a stepped ramp).

Metabo makes non impact drills too, this drill that I speak about is not impact drill, "metabo bs 18 ltx quick" the pulse function is only on some drills.

 

[smilem]

Making a normal cordless drill pulse like that would be rather easy.

Just use a 555 timer to switch the voltage lead (fixed + point) on the speed control potentiometer from its normal positive reference voltage down to ground and back at what ever frequency you want.

By doing that you will have pulse control over the entire speed range of the drill when the pulse circuit is on.

Any schematic ?, sorry I'm rather hard to understand. I have made this other schematic myself by googling some MOSFET motor control examples and 555 timer circuit. However my simulator just blows everything up ;/ could somebody simulate this?

 

[smilem]

This is the drill control switch C3HY-1A-LF1M (makita part 650645)
omron 12A 24vdc

looks like this the heatsink can be removed but the switch is sealed.

https://www.ereplacementparts.com/switch-c3hy1alm-p-201243.html

 

[smilem]

Seems like missed the diode A7 before the PWM switch, back EMF was causing voltage spikes up to 45V and that was the problem, now seems simulate fine. Could you debug it further, I would not want to damage anything.

What mosfet I need? I know I need Resistance Rds(on) lowest possible with enought Amps and perhaps 40V to be safe?