Small generator to run electronics on a drill driven project - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 01:17:17 pm
content: I have a project that will use a drill as it's drive system and requires some power of it's own. I won't have access to the drill battery so, either I use a separate battery or I am wondering if it is possible to buy a small basic generator that will kick out a few mA to run the thing, possibly charging a smaller battery in the unit than what I would otherwise have to fit and have recharged.Does such an item exist or is it even feasible?

author: coppercone2
author_rank: Super Contributor
timestamp: October 10, 2024, 01:21:00 pm
content: its always possible i.e. energy harvesting IC can get you power from nothingwhatever bootleg generator you make, a energy harvesting IC should be able to scrap something out of ityou could just put a random motor attached to your shaft to generate power and see if you got anywhere near your required energythe problem is going to be if you can use the potentially veery low frequency signal if its spinning slow to rectify and boost it properly, but I think some of those IC specialize in harvesting garbage power signals into stable power (random frequency and pulse shape)

author: Andy Chee
author_rank: Super Contributor
timestamp: October 10, 2024, 01:24:58 pm
content: When you say small generator, the smallest that comes to my mind are these old cheap and nasty two stroke generators:I'm inclined to think a battery and inverter would make a much more compact package.

author: CaptDon
author_rank: Super Contributor
timestamp: October 10, 2024, 01:30:25 pm
content: I can't follow your logic here but you are aware that those battery operated drills can use 10 to 20 amps from the 14.4 volt battery pack. What does generating a few milliamps do for you or is this a mains powered drill with some sort of battery powered device monitoring it? We need a better description of your project.

author: coppercone2
author_rank: Super Contributor
timestamp: October 10, 2024, 01:32:22 pm
content: that is useful if you have some mechanical thing you are powering from a drill and it can measure some parametermake those add-on for drills less lamethe most simple one is a RPM measurement circuit if you are driving a gearbox from a drill, or a pump pressure for a hydrualic pump driven by drill, etc, or water flow rate for water driven by a drill (see if your actually pumping a basement out or if your thing is stuck), or an angle gauge for aligning something with a drill (turret, crane, etc)I can think of all sorts of useful shop tools that are almost too lame to be drill powered become borderline useful, if you are SURE you don't need to ever change the batteriesI just imagined a satilite dish you can align with a drill that has a angular readout on it that turns on when its spinning

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 01:43:37 pm
content: I knew this thread would go south this fast.I said mA so no thanks to the petrol popper, I can't put that on a drill. The idea is that this is a drill attachment not a permanent modification to the drill.So I don't know does some company maybe sell pre-wound coils and a suitable cylindrical magnet with a hole in that can go around the shaft connected to the drill. We are talking a tacho here so a sensor, micro controller and LCD. So probably no more than 20mA.

author: Ian.M
author_rank: Super Contributor
timestamp: October 10, 2024, 01:51:15 pm
content: Gear or belt drive to a small stepper motor? Unlike most small hobby motors, stepper motors can generate significant power at low RPM.https://www.eeweb.com/stepper-motor-generator/

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 02:37:00 pm
content: Stepper motor is a good idea but I won't be able to gear it, that is complicating it. I guess the drill will be going at several hundred rpm and steppers are not known for speed so they would generate nicely. Problem is that I would need a small one that has a shaft both ends which makes it a bit cumbersome. The smallest one I found is 65mm total length.I don't know if a cheap BLDC motor will do it but something that small is usually fitted to quad copters so a quite fast and will probably generate little at say 700-1500 rpm.

author: rhodges
author_rank: Frequent Contributor
timestamp: October 10, 2024, 02:43:55 pm
content: Maybe a motor from a floppy drive?

author: Andy Chee
author_rank: Super Contributor
timestamp: October 10, 2024, 02:44:02 pm
content: Ah! I understand your intention now.At first, I thought your project was to power a mains drill from a small generator.But you want to do the reverse, power a small generator from a mains drill!In which case, don't you have access to the drill's mains supply to power your gadget?

author: tggzzz
author_rank: Super Contributor
timestamp: October 10, 2024, 03:01:57 pm
content: Quote from: Simon on October 10, 2024, 01:17:17 pmCaution: domestic freezer motors take 90W when running, but I've measured one drawing 1.2kW for 200ms to 1.2s. 300W inverters invariably trip out.So check if there is a transient 10:1 power draw.

author: Andy Watson
author_rank: Super Contributor
timestamp: October 10, 2024, 03:07:19 pm
content: Perhaps something from the cycling market? A hub dynamo?https://www.sjscycles.co.uk/dynamos-hub/Although, I imagine they will have limited RPM.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 10, 2024, 03:27:44 pm
content: Still baffled and WTF is a petrol popper?

author: SteveThackery
author_rank: Super Contributor
timestamp: October 10, 2024, 03:39:38 pm
content: I'm really sorry because I can't understand what is required. There seem to be two sets of solutions being offered:1/ A small generator that can be driven by the drill2/ A small generator that can drive the drillCould you clarify which is the correct one?

author: SteveThackery
author_rank: Super Contributor
timestamp: October 10, 2024, 03:40:09 pm
content: Quote from: Terry Bites on October 10, 2024, 03:27:44 pmA small two-stroke petrol engine. "Popper" because the poor charge scavenging causes them to fire erratically when not under load: pop, puh-puh-pop pop, pop puh-pop..... You get the idea!

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 10, 2024, 04:09:56 pm
content: The other type of bike light would be like this one. (To scavenge parts from) Much less drag than those old school ones we had as kids in the 70's. Not sure if the drill shaft RPM would be too fast for it though.

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 04:20:03 pm
content: Quote from: Andy Watson on October 10, 2024, 03:07:19 pmThey look lovely, not so much the price.

author: SteveThackery
author_rank: Super Contributor
timestamp: October 10, 2024, 06:20:26 pm
content: Quote from: edavid on October 10, 2024, 03:54:58 pmActually I did, two or three times. It was@Andy Cheewho realised we were all offering solutions to the wrong problem.

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 06:24:28 pm
content: I have amended the post to make it clearer.

author: TimFox
author_rank: Super Contributor
timestamp: October 10, 2024, 06:31:51 pm
content: These people have small cheap generators (not overly-well specified):https://sciencekitstore.com/bicycle-electric-generator-bicycle-dynamo-6-volts-3-watts/

author: Gyro
author_rank: Super Contributor
timestamp: October 10, 2024, 06:41:41 pm
content: Apart from the low cost, you'll probably find those tyre rim friction type dynamos a better match to a drill speed than the hub type (just thinking in terms of the relatively low rotation speed of a bicycle wheel). If it's a one-off project, there are a whole bunch of them on ebay.

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 07:45:16 pm
content: No, it will be a production item.

author: Analog Kid
author_rank: Super Contributor
timestamp: October 10, 2024, 08:10:32 pm
content: I'm curious about the ultimate intent of this project, if you don't mind answering that.I get it that the idea is to generate a small amount of electricity from a cordless drill, without access to the battery. But why? What would this be able to power? Asking because it doesn't seem too practical to me, but since I'm ignorant of your ultimate purpose, I could be wrong about that.

author: Simon
author_rank: Unknown
timestamp: October 10, 2024, 08:47:48 pm
content: well the speed of the drill needs measuring. So a display will show this, not much power is needed for that.

author: Analog Kid
author_rank: Super Contributor
timestamp: October 10, 2024, 08:51:42 pm
content: So you're powering a small tachometer?

author: IanB
author_rank: Super Contributor
timestamp: October 10, 2024, 08:52:57 pm
content: You could almost use a purely mechanical solution, like an old-school car speedo?

author: Gyro
author_rank: Super Contributor
timestamp: October 10, 2024, 08:55:34 pm
content: You're building a tachometer? You can buy those, contact and non-contact.

author: The Soulman
author_rank: Super Contributor
timestamp: October 10, 2024, 09:58:05 pm
content: Quote from: Simon on October 10, 2024, 08:47:48 pmWill the drill be doing actual work (drilling things, drill stuff..) with your device attached?Or is your device the only thing that is attached to the drill, for verification or adjustment of the no-load rpm?

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 10, 2024, 11:36:16 pm
content: Quote from: Simon on October 10, 2024, 08:47:48 pmHmmm... This is where magnets on the shaft driving coils would work quite well. The alternator output can then be used for both power generation and RPM measurement.Or, a variable reluctance type like the PDF attached:

author: Buriedcode
author_rank: Super Contributor
timestamp: October 11, 2024, 12:35:33 am
content: Yeah, its amazing how a few diferent replies throw words out that can skew what people think the OP is asking for.I guess the term "generator" whilst perfectly apt, causes people to think ofmainsgenerators. Dynamo - to me at least - makes me think of the much lower power "generators" that generate pulsed DC instead of AC due to commutator. And "alternator" is what people associate with cars, despite it being a generic term for AC "generators".Some questions:- what kind of display? LCD can use a miliamp or two, 7 segment displays, 10's of mA due to multiplexing, or higher depending lighting conditions.- Assuming you just have a rotating shaft (we'll ignore calling it a drill for now) - what is the min/max speed of this in RPM? Is it constant or will it vary greatly?- Any space constraints? Are you ok with the shaft going through a box thats say 20cm long, or would you rather a small collar with the dynamo in it, wired to a seperate display box?I know thats specific, but as the replies have noted, you could go anywhere from "magnet on shaft, crappy homemade coil" to "guts of brushless motor" to a full on efficient dynamo.Sounds like you have a fairly limited range of RPM, with enough torque that driving a dynamo won't affect it, and only need say 10mA @ 5V max.Simplest I can think of based on all my assumptions: a small DC brushed motor, with a rubber rimmed wheel (tyre from a toy?) mounted against the shaft.Then a recitfier + cap into a simple linear regulator to limit the voltage into a supercap - assuming you don't need this thing to function before the shaft begins turning?A small graphic STN LCD can run off 2mA and be daylight readable if its reflective, and a micro to read the tach signal straight from the little motor.All depends on time, cost and lots of other constraints like reliability, enviroment, and any safety requirements.

author: Simon
author_rank: Unknown
timestamp: October 11, 2024, 06:17:46 am
content: Quote from: Buriedcode on October 11, 2024, 12:35:33 amA traditional bicycle dynamo is an alternator.No I am not making a tachometer directly, don't tell me that I can buy one off the shelf, we know all that already, have done it before, they look shit and cost a lot of money and don't quite do what I want.So to stick to the topic, I am looking for something small/compact that will generate less than 0.5W to top up a battery in the device.

author: SteveThackery
author_rank: Super Contributor
timestamp: October 11, 2024, 08:50:41 am
content: Hey,@Simon, could you answer@The Soulman's question: will you need the drill to still work as a drill when the device is attached? It doesn't sound like it, but wanted to check.

author: nali
author_rank: Frequent Contributor
timestamp: October 11, 2024, 09:00:46 am
content: Quote from: Simon on October 11, 2024, 06:17:46 amHere you are (unless there are other criteria you haven't posted yet?)Micro Alternator (CMC-30R)QuoteFrom your China supplier of preference

author: Phil1977
author_rank: Frequent Contributor
timestamp: October 11, 2024, 10:15:57 am
content: If you have a really power-economic logic, you could even try a small PV-cell or a small vibration generator. Then you don't need a fully turning axis, you could just put a small magnet on the drill chuck.Or place two (for balance) small magnets on the drill chuck and place an induction coil at one side of it.Just think how small the PV-cell on some pocket calculators is. A LCD-display with some simple logic circuit really does not need much power.

author: Simon
author_rank: Unknown
timestamp: October 11, 2024, 01:32:54 pm
content: Quote from: Phil1977 on October 11, 2024, 10:15:57 amYea, I was thinking of just magnets and coil(s)' I was wondering if anyone had done something like this and knew how easy or futile it is before I try.

author: SteveThackery
author_rank: Super Contributor
timestamp: October 11, 2024, 03:39:09 pm
content: One thing I was wondering is how to fix the stator from rotating. It would need to be held by the hand, or else it would need to attach to the drill body, or at least touch it somehow. The latter might be complicated because drill bodies are all different shapes. Or is this designed to fit on one specific model of drill?

author: coppercone2
author_rank: Super Contributor
timestamp: October 11, 2024, 03:48:51 pm
content: I imagine you should get within +-100% of the output of a similar motor to your DIY generator

author: Phil1977
author_rank: Frequent Contributor
timestamp: October 11, 2024, 04:52:58 pm
content: Or take a brushless drill and monitor the VFD output...

author: Simon
author_rank: Unknown
timestamp: October 14, 2024, 06:59:37 pm
content: The goal is to not interfere with the drill at all. Holding the stator will be the problem of the equipment designed. The stator will be part of it.

author: SteveThackery
author_rank: Super Contributor
timestamp: October 14, 2024, 11:15:25 pm
content: Quote from: Simon on October 14, 2024, 06:59:37 pmOK. It's just that you described it as a drill attachment. They aren't typically attached to anything else apart from the drill, hence the need to hold the stator using the drill case.Anyway, you've obviously got a clear idea of what it will look like in terms of its physical realisation, so that's cool.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: October 15, 2024, 12:00:44 am
content: Quote from: Simon on October 11, 2024, 01:32:54 pmIf you want 'magnets and coils' and some Drill coupling, then why not just use a Dual Shaft Stepper motor ?I can quickly find those down to 28mm motor thickness 35mm body and 4.5mm shaft out both sides.

author: Simon
author_rank: Unknown
timestamp: October 15, 2024, 08:07:45 am
content: Quote from: PCB.Wiz on October 15, 2024, 12:00:44 amYes, that was suggested earlier and is a really good idea although the total length in this case does start to became a problem in the design.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 15, 2024, 08:44:16 am
content: How will you be mounting it? Can you use a jelly-bean 3-phase drone motor (outer drive), 3D print a TPU wheel around it and push it against the spindle?When rectified there will be plenty of power, 3 phase so quite smooth already? And the breakaway torque won't be that high in contrast to stepper motors.

author: 404notfound
author_rank: Newbie
timestamp: October 15, 2024, 09:22:29 am
content: Hello,Making a generator, with the rpm of a drill, with a low cost and / or custom will be difficult.You have to use a SS41F with magnets for the tachometers and a small CR20 or other to power the arduino and the LCD screen.Add more magnets poles if you want to increase resolution / ACC in transient Space.