DIY Rotomat: Building a Budget Device with Disco Light Bulb Motor, 230V Input, & LED Alternatives

Hello.
For some time I have been planning to build a simple, cheap rotomat. One that it would be useful, and the funds are limited, and two (and probably more here) that I'm curious if I can do it, because I like DIY. However, I have huge gaps in electrical knowledge.

I took into account various solutions regarding the drive (old tape motors, cheap rotating display, microwave platter drive motor / has a nice function that it turns in a different direction each time it is turned on / etc.).
Now I have the drive system in my hand ... a disco light bulb.

rotomat...jpg Download (118.85 kB)

But this is where the questions come in. There is 230V to the system, 10.5V at the output of the PCB with the transformer, and only 2.7V at the input to the motor. There are 3 more colored LEDs along the way. As they are naturally unnecessary, what should I solder instead of them so that the motor gets the right voltage (some resistor?)? And are the cables at the board input too flimsy to provide 230V? Such were the factory ...

Another question is the possible magnetic field. There is no problem that most of this contraption is in a separate housing closer to the plug, but the motor must be next to the watch. The question is, how can a strong magnetic field produce such a weak motor (motor parameters unknown)? The watch itself is some distance from this motor (taking into account the motor mount, the device case, the axis of rotation, the second case which the watch will be in, etc.) so maybe this is a safe distance ...
The magnetic field can of course be checked with a meter, but it is again an investment and not knowing what values are considered safe for the watch and which are not.

So far I have worked on the first prototype. Everything works fine, but:
1) I do not know what to replace redundant diodes
2) I am not sure there is a possible magnetic field and hence I am concerned about putting a mechanical watch there


So far it looks like this:

rotomat...jpg Download (226.19 kB)

rotomat...jpg Download (201.25 kB)

rotomat...jpg Download (195.52 kB)

rotomat...jpg Download (188.85 kB)

rotomat...jpg Download (155.28 kB)


Costs so far:
- mechanism removed from the rotary bulb - PLN 6.00
- construction made of Constructor elements (a toy from my childhood, 1987) - PLN 0.00
- cables from private supplies after broken devices - PLN 0.00
- housing after an old burnt electronic transformer - PLN 0.00
- a can of an old watch - PLN 0.00
- soldering tin, heat shrink bands, cable ties, electricity, my work, etc. - I don't know ... PLN 0.00

I am skipping the issue of the housing, finish and the switch as the next stage.



Please help me replace the diodes with something that will lower the voltage in front of the motor and how to measure or eliminate any magnetic field around the watch.
Thank you in advance.

PS I have already asked at Zegarkiclub.pl.

There is a transformer on the board, so probably the current from the mains is very small, and the cables for such current are thick enough with a large margin; a separate matter if their insulation is sufficient for 230V, but I have already seen a thinner one, which was supposed to withstand a few thousand V - this one would have to be botched if it did not withstand 2000V, and the mains voltage all decent insulation materials withstand already at a thickness of 30u, the best at 5u (such a normal, not particularly thick hair is 50u); the problem may be rather mechanical damage to the insulation or the wire core.

The motor will spin faster when higher voltage is applied. And what voltage will be safe for it, it is difficult to predict - with a dozen or so volts, the risk may be high speed causing excessive wear of the bearings, or even their breakdown - but it obviously depends on the motor. In addition, stopping the motor connected to low voltage by force does not pose a threat, with a higher current of the stopped motor, it will be greater (without braking, the motor only takes the current needed to overcome the resistance to motion) and it will quickly overheat. And in general, you need to have the parameters of the motor matched to the application - the question of how much it fits, maybe there is a rating plate on it, if not, then you need to take measurements.

As for the measurement of the magnetic field: take a piece of wire (20cm) made of mild steel - it must be steel that is attracted to the magnet but does not magnetize permanently (in the past, a suitable wire was used to seal milk cans at the time when it was brought to the store milk in cans and poured out to customers - it was cheaper than the one in sealed bottles, so you came with your own vessel and the saleswoman poured; today maybe a long and thin nail, but not so hardened) - hang it on a thread, tying it in the center of gravity of this wire (this the wire should rotate freely) and check that the motor attracts it. It can be different, there may be motors that do not give a detectable field, and those that give quite a lot.

It's maybe me about the motor and the way it is powered in such a lamp ...

We have 3 LEDs connected in series to the current driver. The company's lamps use 1W LEDs, yours look 0.5W and this is probably the current forcing the driver.
The power of the motor is taken from motors with a smaller ratio - from one of the diodes (motor in parallel with one of the LEDs - usually red), and with a motor with a large ratio - directly from the driver's output.
When such a motor is powered with 5V and its shaft is stopped (mechanically), the current does not exceed ~ 70mA from what I remember.

The problem here will be the need to load the driver with the rated current, because if the current is lower, the driver will raise the voltage to force the flow of the set current.

As for the construction of the drive itself - Despite the fact that the protruding shaft is aluminum, unfortunately only plastic inside the gear.

And the motor, despite its low power and size, "sows" disturbances, it's sorry.

Justyniunia wrote:

We have 3 LEDs connected in series to the current driver. The company's lamps use 1W LEDs, yours look 0.5W and this is probably the current forcing the driver.
The power of the motor is taken from motors with a smaller ratio - from one of the diodes (motor in parallel with one of the LEDs - usually red), and with a motor with a large ratio - directly from the driver's output.
When such a motor is powered with 5V and its shaft is stopped (mechanically), the current does not exceed ~ 70mA from what I remember.

The problem here will be the need to load the driver with the rated current, because if the current is lower, the driver will raise the voltage to force the flow of the set current.

Thank you for your comprehensive answer, but I must honestly admit that I have read it once and I do not fully understand it (what is a driver?). I don't even know how the diodes themselves are connected, because you can only see that they are all soldered to this circle. The last sentence, however, is completely incomprehensible to me.


If such a motor causes interference, i.e. I understand that it generates a magnetic field, then it is interesting what motors are used in cheap rotomats? Or how they are isolated from the space the watch is in.

Driver is such a specific power supply.
The point is that in order to power this motor from this power supply, these LEDs are necessary.
A much better idea would be to power this engine with an old phone charger, e.g. 5V.

This motor is able to effectively prevent DVBT reception on a room antenna from a distance of several meters. Is this a problem in your case, then you have to answer for yourself.

Just the disturbances caused by the alternating magnetic field do not harm the mechanical watch (is it supposed to be like that? I will not know from the photo of the external appearance), as long as this field does not have a constant component; on the other hand, such disturbances can affect the operation of a watch that has some electronics, e.g. a quartz generator, a generator frequency divider and a synchronous motor to drive the hands, because these disturbances can be counted as additional pulses from the generator and cause the watch to rush . In both cases, the case of the watch can to some extent protect its interior from the effects of interference.

A separate issue: it is not certain that Johnny-T and Justyniunia have the same motors (or even with similar parameters) - manufacturers are able to frequently change device design elements and have no reason to inform about it, as long as it does not affect the functionality of the entire device - even if it is a device from the same manufacturer and has the same name, its internal structure may not be the same; in particular, this applies to the motor - so check it. And I have the impression that so far the author has not written what are the requirements for the operation of this motor - e.g. at what voltage does it rotate at the speed it needs?

There are cheap (a few zlotys) stepper motors with a gear (this one is not a stepper - it has only 2 wires) - if you need a very slow rotation (rotation lasting a few minutes), then such a motor is perfect - but getting rotations faster than 1 per minute is already difficult, maybe even very difficult.

Thank you to everyone for comprehensive statements, however, not all of them are consistent enough to give me a clear answer on the subject.
For this reason (and concerns about possible damage to the watch) I let go of the topic.
Best regards.

You're exaggerating something, buddy. Are you holding the watch close to a working GSM phone?
If so, the signal when connecting with a poor range is many times greater than the noise from the motor. In these bulbs from the poor, the engine has a negligible power and will not damage anything and you can connect it directly to the USB 5V power supply ...