About AC dimmers/speed controllers (“2000W SCR”, Dremel and etc.)

Wow, just bought 5 pairs of carbon brushes and just after replacing the very worn out set in the tool, the speed controller died on me.

As cera@1967 said in the past, this was to be expected.

I am right now wondering if the above mentioned Hilda 180W rotary tool features a God's way speed controller. And not just :???: wondering. If any of you has something worthwhile being said, please do so.

Barkuti the best money I ever spent on a rotary tool was buying a Proxxon. https://www.amazon.com/Proxxon-38481-Professional-Rotary-Tool/dp/B001FWXEO6
I mentioned it before in this thread, but its a seriously professional tool that will last you for a long time. I know it’s not cheap but built better than any rotary tool I have owned. The full wave speed controller works flawlessly. Full roller bearings in the shaft and motor. If you use a rotary tool for alot of different things, then my vote goes to spending a little more and get the Proxxon. Just my 2 cents :wink:

Can understand moderator007, I also love quality. Gear like that will have to wait until I fix my mind programs and I can attract general and financial abundance.

In the meantime, bought the 180W Hilda tool with a proper bag. Had to ask for help for such a thing.

:-)

I did the same setup when my dremel switch went bad, i also went with a lipo battery, but my question is, when i apply too much pressure when sanding, the voltage regulator starts to beep and the motor stops.
any one know what that could be from?
IMG-1581 hosted at ImgBB — ImgBBrc gliders

Smells like some sort of overload protection in the controller; when you increase the pressure when sanding, the engine torque increases and this means more engine input current.

You must somehow limit engine current, or upgrade the speed controller if it is a very annoying problem.

yes that makes sense, thanks for the reply,
if i upgrade the speed controller, would i need to up the W on the controller? any idea? or point me to the right direction which ESC i would need to use.
thankyou

You are providing too scarce information, this doesn't helps. If you were to carefully lay down your problem's information in a single message, the answer would very likely be already in your hands.

What is W? Wattage? Probably, just probably. This is because controllers are rated for voltage and current.

A suitable controller for your rotary tool must meet both its voltage and current input requirements. There is no problem if the controller exceeds well both, and in fact this is preferable, namely the current requirement if going to buy it from china.

In that photo of yours I just see some battery powered rotary tool (7700?), connected to some sort of high discharge li-ion (?) battery. This has to do with the input voltage requirement. From here I can only guess that the battery is 2S.

Suggestion: If 7700, you could get a nice power boost by using a 3S LiFePO4 battery, which could easily deliver around 9V even under load to the tool. The reason to use LiFePO4 is its flat discharge curve or stable output voltage, which means you won't feel the battery going flat as you discharge it, i.e. full output power until the very end or very close.

thanks for the notes, yes i am using a 2s 8.4v 5000mAh lipo battery, and the tool is a very old hand held dremel, the variable switch broke and so i made this, i am familiar with LiFe batteries. I will take your suggestion and give that a try see what happens. thank you

dlgglider, according to the available information I've found about the Dremel 7700 (here and there), the stock tool is like a joke toy. The manual I've found @manualslib.es specifies “200mA” as battery capacity, something I could feel to be completely wrong starting with the fact that 200mA specifies a current figure, not a capacity one. In this Dremel 7700 thread @ Parallax forums someone mentions 800mAh; so a small battery. I guess the battery could probably provide 8 to 12A continuous, just probably. With these figures it is easy to guess that the stock battery should not be able to provide 90W continuous in a reliable way. The stock motor, if designed to last, may be rated for that figure or a little bit more.

I am seeing related ads in AliExpress where similar DC motor speed controllers are rated for 2 to 5 A continuous (this or that), which is small. Or this other one, rated for 10A continuous…

If you go with a higher voltage battery, the higher voltage will allow the motor to reach higher rpm; the current input will also increase. I don't exactly know how a DC motor's impedance varies with input voltage, but as far as I know it remains about constant, which means that every increase in input voltage will also cause an increase of input current of the same magnitude. So if you go with an increase in input voltage, don't go overboard or the engine may not handle it (P = V × I).

This ZK-BMG motor governor is rated for 12A continuous and 20A peak. Costs a little bit more, but unduoubtely looks pretty neat. Or you could go with this another one, which meets all the specs you need very well whether you decide to go with a higher voltage battery or not.

As a side note, remember that if using li-ion or LiFe batteries in series without BMS, in case they go flat it is very recommended to charge them at least a little bit just after that, to prevent any chances of leaving a reversed cell in the battery.

Barkuti, thank you for the long and informative reply, makes total sense, in fact im using a 3000mAh battery on this now and it must be over dumping and shutting off the unit, it must be a security thing, but looks like i might need a new dremel anyways as it its difficult to hold this one while the battery dangles lol

i also have a voltage checker attached to the balancing lead, this way i know not to take each cell down below 3.2 volts.

In my opinion and experience cutting off at 3.2V, although no problem, is a tad high, particularly if under load which I guess you don't check.

I've scavenged some 18650 battery packs in the past, succesfully recovering a few cells lying below 2V (1.6 - 1.7 V) in a particular case (Samsung 26C cells out of a 6-cell pack), although I discarded two of them after a self-discharge test of a few weeks. If you were to ask me, I'd tell you that down to 2.5V is completely fine, particularly for quality batteries.

If you want to prolong the life of your li-ion batteries, it's not really about avoiding the lows… it's about avoiding the highs.

If interested, read BU-808: How to Prolong Lithium-based Batteries @ Battery University. Lots of wise information there.

A brand new laptop battery should succesfully deliver hundreds of cycles. However, in practice most of these batteries are kept always fully charged inside the laptop, something which kills them. I know this from experience.

i forgot to mention, the battery i speak of is a LiPo, which the lower cut off is 3.2v, i know the 18650 batteries can be taking down further, but LiPo the low cut off should not be lower than 3.2, actually 3.8 should be the low discharge

Where did you heard such a thing, and what tells you that is correct?

3.2V can be used as a cut-off value, although it can be considered a little bit high, particularly for a BMS which must cut-off under load. 3.8V, though, is straight out wrong.

There is not that much of a difference between li-ion and li-polymer, and it certainly has nothing to do with the cut-off values you can use.

Check out lygte-info.dk. It is a site dedicated to tests of electronic devices and batteries. Henrik, the site's owner, has done hundreds of battery tests. He usually cuts-off at 2.8V for li-ion and 2V for LiFePO4, and the shape of the tests curves and the different rate of each discharge curve allows you to see the energy remaining for any given cut-off value (at or above 2.8V, that is). Examples:

This LiitoKala cell is actually manufactured by Power Long Battery (at first they started selling it to consumers in their original wraps).

Not much else to say. You can keep cutting off at 3.2V, but now you know (or you should) there is no problem if you go lower.

The way I believe and my experience tells me I am right. I rarely, if at all, need to replace a smartphone battery. And I keep my smartphones for many years, cycling their batteries well above a thousand cycles, or more. But 0 to 65%, as a rule. This means my smartphone battery (4.35V type battery right now) lays at ≈4V without load (i.e. the minimum load of the battery monitoring software and the smartphone while sleeping, tad less than 30mA or so) just after I stop the charging process. As I said, it's the high voltage or high state of charge what you must avoid if you want to ensure ultra long life for a li-ion (or li-poly) battery.

Hello fellows,

Very recently I had the “pleasure” of repairing a Dremel 3000 making use of one the above generic parts coming from AliExpress.

Let me show you a couple related pictures:

Note: ignore the thickened rods at the end of the coils, that is a modification I did because of reasons. They actually are much thinner, meant to insert inside holes at the original speed regulator.

I had a few words with thefreeman about this matter more or less recently, about the input coils you can see in the pictures. Nothing conclusive, though, I was then thinking that the purpose of the coils probably was to increase the power factor of the tool.

At this point though, I think their purpose is to reduce or eliminate the noise from the triac-based regulator, while I also do not discard the power factor benefit; I would love to hear more experienced fellows in these matters, though.

Here is a related thread: Power main distortion from TRIAC dimmers, what can I do to get rid of it?? @ EEVblog

And more:

Conclusions.-

The Dremel brand “gangsters” deliberately designed the speed controllers of their tools to break over time. After all, they are triac based and unsuitable for driving electric motors unless some sort of snubber circuit (?) is used.

But back to the mains distortion issue induced by these controllers, how do you experts think we could reduce or negate it? This is mentioned in the above aforesaid EEVblog thread. A couple of coils at the input and output, like in the above Dremel 3000? I wonder about the proper rating for the coils (amount of henries). Would stuff like these “5Pcs 10mH 4A Annular Common Mode Filter Inductor Choke Toroid 0.6 Wire 14x9x5mm” or these “5pcs toroidal common mode choke 9MH filter inductor 18x10x10mm magnetic ring” be of any adequate service?

Cheers :-)

Hello! :-)

I recently bought a couple of these dimmers, one of this kind and another one based in the BTA41-600B from here:

I was hoping to be able to measure the average output voltage of these “governors” with my cheap multimeter (this type) in AC voltmeter scale, but it doesn't works, all I see is ≈230VAC in the multimeter's screen no matter where the potentiometer is set at.

Any suggestions? Besides buying an :)) oscilloscope, that is.

Thanks and regards everyone.

Hi!

I had one (not your model posted) that didn’t dim, still at max even rotate the pot.
Then checking the TRIAC I found that was bypass, two of their pins were bridged on pcb traces by a solder blow.
Fixed this mistake now work properly, hope you can solve

Salvador, i think your dimmer may be broken.

i have a light dimmer like that which is always full ON no matter the setting of the dial. Maybe that is a default failure mode.

To see the gate control will likely require an oscope.

Best wishes and good luck sorting it out.

Thanks for the comments fellows.

I just tested the TRIACs in both modules using information from How to Test TRIAC with Multimeter @ Inst Tools. Long story short, the TRIACs work correctly both ways. When I connect the gate of the TRIAC to MT2 the diode voltage drop is very low, like ≈0.07V (compared to ≈0.45V for an old 3A rated 1N5404 diode I had lying around), but I guess this is pretty normal because these TRIACs are composed of two very beefy diodes. The first two digits in their “part numbers” (BTA16-600B and BTA41-600B) are their average maximum current ratings in amps.

Yeah but 0.07V forward diode drop sure seems like a shorted diode, just sayin’

I don't think they are shorted, I'm pretty sure they are working correctly. The thing is that the multimeter is pushing sub-mA currents through these massive, dozens of amps rating diodes, and so the Vf is super low at such current level. I have tiny diodes here and their displayed Vfs are way higher when tested with the multimeter.

Now, the answer to my question is here: Would analog multimeters measure correct dimmer's output? @ Electrical Engineering

In essence, my lame-ass cheap multimeter can't measure the average RMS output from the dimmers, as the waveform is far from senoidal. For this reason I am going to grab a proper analog AC voltmeter, Young Frankenstein :-)) style. Or I could also get one of those Voltcraft VC-155 multimeters. These will do the job properly.