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Running a cordless drill from an AC transformer

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Re: Running a cordless drill from an AC transformer

Postby sunnybob » 10 Dec 2020, 06:54

Back in '89, I was the secretary of a target shooting club. I bought 5 turning target units that were using windscreen wiper motors They had huge torque, snapping a man sized target frame through 90 degrees almost as fast as you could see. They ran off full sized car batteries that in the end I rigged up to be on permanent trickle charge because the targets drained the batteries so quickly.

Its all about the torque, so DO NOT under estimate 12 volt dc power requirements. :shock:
8-)
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 10 Dec 2020, 07:51

Your link produces only a page full of code when I click on it, Bob. Obviously it works for others, though.
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 10 Dec 2020, 08:02

sunnybob wrote:.........DO NOT under estimate 12 volt dc power requirements.......


Don't forget that I have the drill's gearbox at my disposal, and the torque control. If there is too much torque required the torque control will ratchet. If it is too much of a strain in the faster gear, I'll use the slower one.
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Re: Running a cordless drill from an AC transformer

Postby sunnybob » 10 Dec 2020, 11:47

I think your biggest problem will be the continued torque.
When a drill first starts up there is high load for a fraction of a second, then it basically runs at a fast idle while its being used.
Operating a screw drive mechanism attached to a considerable weight and friction of moving parts is putting continuous high load. And dont forget on the way down the weight will be trying to make the motor go faster.

I applaud your efforts, and I'm no stranger to sticky back plastic and toilet roll construction, but I am concerned you are putting all this stuff out of sight and in a flammable cabinet.
Stay safe. 8-) 8-)
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Re: Running a cordless drill from an AC transformer

Postby AJB Temple » 11 Dec 2020, 02:28

Is this set up not basically the same as an electric window lift mechanism in a car?
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Re: Running a cordless drill from an AC transformer

Postby RogerS » 11 Dec 2020, 05:53

AJB Temple wrote:Is this set up not basically the same as an electric window lift mechanism in a car?

The switch action is different...at least on my car...might be the same on a Tesla :D

Mike wants to press the same pushbutton switch to go up (if the TV is down) or down (if the TV is up). In my car I have a toggle switch.
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 11 Dec 2020, 08:15

....and I don't want it to stop in the middle, nor to have to keep holding the switch whilst the thing is in motion.
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Re: Running a cordless drill from an AC transformer

Postby AJB Temple » 11 Dec 2020, 11:30

Even Tesla has a toggle switch. Musk did not specify voice control for the windows. But I think all cars have a single press for all the way up (or down) and either hold or press again to stop part way.

Really I feel this needs a remote control solution :lol:

We also need to remember that Mike has a sore finger and may need to factor that into his design.
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Re: Running a cordless drill from an AC transformer

Postby sammy.se » 11 Dec 2020, 12:12

this is a very interesting thread. Curious to see the end result.

Just a thought Mike: what if the Tudor rose pivoted on a horizontal axis, so that you push the top half to go up, and the bottom half to go down? it would mean a slight taper, or bigger gap around the rose...

It is not as neat as the solution you envisage however.
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 11 Dec 2020, 15:47

I looked at that, Sam, because that would better suit a toggle switch. However, as you rightly point out, that would make the gaps around the carving a bit too obvious.
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Re: Running a cordless drill from an AC transformer

Postby 9fingers » 11 Dec 2020, 15:51

A proximity sensor would have been ideal. Just touch an area but no need for it to move but being active, it would need power (very low) to be applied all the time.

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Re: Running a cordless drill from an AC transformer

Postby Sheffield Tony » 11 Dec 2020, 15:55

AJB Temple wrote:Really I feel this needs a remote control solution :lol:


Need an IR receiver to detect the TV remote power on signal, and raise the TV automatically for you. Perhaps a strategically placed IR transmitter too to relay the power on signal to the TV inside the cupboard so that it can be "warming up" as it rises.

Isn't it ironic that as a kid, we had valve TVs that you had to turn on ahead of time; they had to warm up. Then for a while we had the luxury of TVs that came on almost instantly. Now we are back to turning them on ahead of time; they need to boot up.
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Re: Running a cordless drill from an AC transformer

Postby novocaine » 11 Dec 2020, 16:25

And back we go to complex solutions. :)
the battery will run on 12v just fine (or should if the confuser doesn't have a low voltage shutoff)
so a 12v 4amp regulated power supply would be ideal.
this should do it
https://uk.rs-online.com/web/p/embedded ... s/1065830/

you are going to have take the drill apart and look at how the forward/reverse works. some move the contact on the switch others move a separate switch. either will be fine but as you are going to be bypassing it all you'll need to look at how.

next you'll want to wire your toggle switch to account for how it reverses directions, that could be tricky if it's a separate switch, bit easier if it's shifting contacts in the trigger.
I'm afraid you will be doing a bit of wiring and soldering to bypass it all, do not bypass the brain box, it's doing all the PWM for the motor speed control.

good luck, I hold no responsibility for when it goes wrong. :D
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 11 Dec 2020, 16:36

That's pretty much exactly what the plan is, Dave.
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Re: Running a cordless drill from an AC transformer

Postby novocaine » 11 Dec 2020, 16:39

Mike G wrote:That's pretty much exactly what the plan is, Dave.


I didn't see anywhere that recommended a power supply, although I could have missed it. :) was trying to be helpful instead of stepping on peoples toes, honest guv. :D

might want to check the speed of the drill at full chat, could be a bit sharpish on the up. (yes even on low speed)

thinking first tele to be launched to space without a rocket. :D
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 11 Dec 2020, 17:13

ALL posts are helpful here (and gratefully received), in that this is an area of weakness in my DIY armoury. Anyway, this is the basic kit of parts I'm working with:

Image

Image

Plus of course wire, solder, and so on. My soldering is somewhere closer to adequate than competent, but good enough. I hope.

I'm planning on making a start on this over the weekend, and the first thing I'm going to do is wire power to the drill and pull the trigger.
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Re: Running a cordless drill from an AC transformer

Postby sammy.se » 11 Dec 2020, 18:47

Electronics is also a mystery to me.
My soldering improved when I bought some proper flux, just in case you don't already have some. it's very helpful.
https://www.amazon.co.uk/flux-soldering ... 01N6B6E9W/
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Re: Running a cordless drill from an AC transformer

Postby Lons » 12 Dec 2020, 16:31

sammy.se wrote:Electronics is also a mystery to me.
My soldering improved when I bought some proper flux, just in case you don't already have some. it's very helpful.
https://www.amazon.co.uk/flux-soldering ... 01N6B6E9W/

In my case the improvement was after buying a soldering station so I can control the temperature, Makes it much easier, plus the correct flux and solder.
I have a degree in faffing about (It must be true, my wife says so)
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 13 Dec 2020, 17:08

Some actual progress to report, and a question or two.

I took the drill apart:

Image

That's power in from the battery at the bottom right, and next to it is some odd bit of aluminium......back to that in a minute. Furthest left is the battery read-out thingy. These all connect to the switch unit, and thence just 2 wires to the motor.

On the top of the switch unit is the reverse switch. This is crucial to my plans, and it's not very convenient:

Image

The first job was to ascertain that everything worked, so I rigged up the motor to the power unit, and pulled the trigger:

Image

It all worked beautifully. The output of the AC to DC transformer only registered 2 out of three lights on the battery strength meter thing:

Image

That's with the little dial controlling output on the transformer cranked up to maximum. But the speed of the motor looked fine to me, and it has plenty of torque (I couldn't stop it with my bare hands).

I pulled the main switch permanently on, then rigged up the pair of 2 way micro-switches and ran it again, and that all worked perfectly. Every change to one switch or the other changes the state of the circuit:

Image

Image

In principle then, the electrics of this lift thing are going to work.

OK, so my questions. What is this thing? Is it some sort of heat sink? If so, why?

Image

And secondly, the reversing switch. The drill one has a tiny little plastic lug/ pin on the top and a relatively stiff mechanism. This isn't going to last 5 minutes in any mechanism I am planning to make. So, I want a 12v double pole switch with no neutral position (ie on/ on reverse). Can anyone tell me precisely what these things are called?
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Re: Running a cordless drill from an AC transformer

Postby Robert » 13 Dec 2020, 17:27

Your mystery gadget is probably the variable speed controller and yes the electronics is mounted on a heat sink. And I think you are looking for a DPDT switch - double pole double throw. should say if it has an off position or not. may also say 'changeover' switch as there is no off.
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 13 Dec 2020, 17:32

Thanks Robert. As I don't need variable speed control, can I just cut this away, and wire between the two terminal it comes from?

I've found a switch which looks as though it would do the job:

https://www.amazon.co.uk/Pxyelec-Motor-Polarity-Rocker-Switch/dp/B07FJLMCFD/ref=sr_1_3?dchild=1&keywords=reverse+polarity+switch&qid=1607876809&sr=8-3

Anyone know something better, or any good reason why that one wouldn't work?
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Re: Running a cordless drill from an AC transformer

Postby 9fingers » 13 Dec 2020, 17:35

The item on the heatsink is quite likely a MOSFET - a sort of transistor and both it and the cooling of it are VITAL so dont be tempted to discard or damage it.

The switch you want is a two pole changeover switch but it MUST be capable of high current when switching DC. IGNORE any AC current ratings
Look for ones designed for automotive use for better chance of being man enough for the job.

There is a risk that switching the motor direction without removing the power will blow up the controller. This is why drill switch mechanisms are interlocked to only allow direction reversal when the power is off.
This could muck up your entire project in a trice.

HTH
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Re: Running a cordless drill from an AC transformer

Postby Robert » 13 Dec 2020, 17:36

I O II implies a centre off position. You also need to consider switch design as in what the lever looks like and how far it has to move.

And I'd try bypassing the entire drill switch wiring rather than go cutting wires. Full speed will still go via the speed control.
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Re: Running a cordless drill from an AC transformer

Postby Mike G » 13 Dec 2020, 17:42

9fingers wrote:.......There is a risk that switching the motor direction without removing the power will blow up the controller. This is why drill switch mechanisms are interlocked to only allow direction reversal when the power is off.
This could muck up your entire project in a trice......


I know, Bob. The mechanical over-centre rocker thing that will sit on the shelf edge will trigger the off switch before it triggers the change direction switch. Its exact design will depend on the switches I am working with, but the principle is pretty simple. I guess if it would help if I drew it.
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Re: Running a cordless drill from an AC transformer

Postby 9fingers » 13 Dec 2020, 18:13

Mike G wrote:
9fingers wrote:.......There is a risk that switching the motor direction without removing the power will blow up the controller. This is why drill switch mechanisms are interlocked to only allow direction reversal when the power is off.
This could muck up your entire project in a trice......


I know, Bob. The mechanical over-centre rocker thing that will sit on the shelf edge will trigger the off switch before it triggers the change direction switch. Its exact design will depend on the switches I am working with, but the principle is pretty simple. I guess if it would help if I drew it.


OK if your design ensures that the motor has stopped before the direction switch is moved then you should be fine.
I'm torn between suggesting that the controller is abandoned completely and your power on/off switch controls the mains into the power unit or that you continue as you are.

You hopefully can see parallels when we ask building type questions and you feel a certain "I would not have started from there" feeling :lol:

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