Easiest way to control current

Thread Starter

Jpfaff40

Joined Feb 20, 2019
7
I have a problem and I can’t figure it out. I work in a clock shop and we buy pendulum swingers to imitate the movement on one from mechanical. The problem I’m having is that i tried different potentiometer from 10k to 150k and there all doing the same thing. I use the sweeper leg and another one on the positive lead. Is there something else I could do or use. I took electronics in school 20 years ago and forgot a lot. They use 2 c batteries in parallel. On narrower grandfather clocks the pendulum strikes the sides. If I turn potentiometer up it hits the sides. If I barely turn it down it stops. Any help would be a appreciated thank you.
 

WBahn

Joined Mar 31, 2012
24,850
It's very difficult to tell what you are trying to accomplish OR how you are currently trying to accomplish it.

Could you provide a schematic of what you are currently doing?

Could you describe what these "pendulum swingers" are and how they work and how you control/adjust them?
 

Thread Starter

Jpfaff40

Joined Feb 20, 2019
7
The swingers have a battery supply consisting of 2 c cell batteries that run to a little chip. They apply full voltage and current. Through trial and error i put various pots on the positive lead coming out and attached to outside leg and input to swinger on the center leg.
 

Thread Starter

Jpfaff40

Joined Feb 20, 2019
7
This is a pick of the swinger in question. Vary case widths require less swing. What would be the easiest thing to do. Any more questions feel free to ask. Hope this helps.
 

WBahn

Joined Mar 31, 2012
24,850
You say that all of these pots you are putting in are doing the same thing, but then you describe what sounds like different things happening as you change the pot setting.

. It might help if you clued us in to, exactly, what they are all doing?

It sounds like all you have done it put a resistor in series between the batteries and the IC-controlled driver circuit. That's likely to do all kinds of things other than what you want.

How about looking up the manufacturer's information about the swingers you are using?
 

DickCappels

Joined Aug 21, 2008
5,930
Just a hunch: Your pot sounds like a very large resistance for this sirt of application. Try simething much mower like 500 ohms or 1 k.
 

Yaakov

Joined Jan 27, 2019
1,601
The swingers have a battery supply consisting of 2 c cell batteries that run to a little chip. They apply full voltage and current. Through trial and error i put various pots on the positive lead coming out and attached to outside leg and input to swinger on the center leg.
IF you are trying to control the excursion of the pendulum you may not have much success by limiting the voltage form the battery. The active electronics involved require a minimum voltage, and from the look of it, I am guessing that it uses something like a 555 to periodically charge that large capacitor and discharge it into a coil for the swing. I think it might sense the pendulum midpoint and "kick" it, like one of the various desk accessories that does the same thing.

If you are, as I am speculating, putting the pot inline with the red wire from the battery, the device is just going to see a weak battery, which, if it is well designed, shouldn't affect the operation until it reaches a critical point and simply stops.

But, as others have said, you are not providing enough information. If you could 1) explain the change you want too make (e.g.: less excursion, a change in period, etc.), 2) draw a picture of what you are doing, and 3) describe what happens when you operate the pot, you are more likely to get help.

Good luck.
 

Thread Starter

Jpfaff40

Joined Feb 20, 2019
7
I would like to simply slow down the the swing of the pendulum. A guy who was a industrial electrician said using the pot I had the right idea. When the pendulum is closest to the positive leg it swings full strength and hits the side of the case. When I turn it down just a little bit it slows down then completely stops. The pic I posted is the exact swinger we use. I guess my question is what can be done to keep the same voltage yet have good control over the current
 

Yaakov

Joined Jan 27, 2019
1,601
I would like to simply slow down the the swing of the pendulum. A guy who was a industrial electrician said using the pot I had the right idea. When the pendulum is closest to the positive leg it swings full strength and hits the side of the case. When I turn it down just a little bit it slows down then completely stops. The pic I posted is the exact swinger we use. I guess my question is what can be done to keep the same voltage yet have good control over the current
Are you trying to reduce the voltage from the battery? I don’t think this will ever work.

I think you are going to have to reduce the voltage to the coil that actuates the pendulum. The best way to do that will depend on the circuit they are using. If a pot is going to work anywhere it is most likely to be on the input to the coil, but that will waste a lot of battery if there is a specific place to control the power to the coil in the circuit without just turning it to heat.

We are working nearly blind here. If you could take clear photos of the circuit board front and back, you might find more help.
 
Last edited:

AnalogKid

Joined Aug 1, 2013
8,137
Please provide more information.

What is the value of the pot you are using (do you really think this isn't important?)? Better yet, what are all of the markings or stampings on the pot? Letters are important.

Please post a link to the vendor, or the manufacturer. Three sources I found all say the device uses one D cell, not two C cells. Also, please post a close-up photo of the pc board.

The system is an electromagnet that gives the pendulum arm a little tug or push as it goes by to overcome friction. While reducing the voltage to the pc board will reduce the strength of the magnetic pulse, by the time you have the voltage down low enough there is not enough to run the timer chip. As above, the pot value you have is way too large. The current pulses certainly are 100 mA or more, maybe as much as 1 A. You probably want to start with something like a 10 ohm wirewound pot. A 4.7 ohm fixed resistor should give us a clue.

ak
 
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Tonyr1084

Joined Sep 24, 2015
3,636
I'm with @Yaakov on this one. Putting any form of resistance into the power supply will not change the period or intensity of the swing. Since it is battery operated you need to understand that as the batteries lose power the voltage drops. Yet the device continues to work until the battery voltage is so low that it can no longer function. By putting a resistor in series with the supply (batteries) you're simulating a dying battery. If you want to change the intensity of the swing then you're going to have to change something on the board. Without a schematic we can't begin to guess at what is needed.

Assuming you have a magnetic coil driving the swing you have to change the current at that point and not at the power supply. And without knowing more about the circuit I'm willing to guess that a pot in series with the drive coil may not be capable of handling the amount of current the coil pulls. Here again we need to see a schematic. Or at the very least some really good closeups of both sides of the board.
 

shortbus

Joined Sep 30, 2009
7,074
IF you are trying to control the excursion of the pendulum you may not have much success by limiting the voltage form the battery.
If that is what he is trying to accomplish your correct. Here is information from another company selling these, that addresses how to make the swing shorter.

Swing adjustment: This device is operated by an electro magnet that is positioned between two magnets that are on the pendulum arm. If the swing of your pendulum is too wide, then you can put a piece of tape over one or both of the magnets to reduce the width of the swing of the pendulum.

From - https://www.clockworks.com/clock-repair/largependdrive-clock-instructions.html
 
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Alec_t

Joined Sep 17, 2013
10,429
I would like to simply slow down the the swing of the pendulum.
Then increase the length l of the pendulum. The natural period T of a pendulum is given by the equation T=2π√(l/g).
Judging by pictures of your driver mechanism, I think the drive circuit for your pendulum is a variant of this single transistor type. The margin between working efficiently and non-working for that circuit will be narrow. Reducing the swing amplitude significantly would likely reduce the induced pulse to the transistor base and hence stop oscillation.
 
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Yaakov

Joined Jan 27, 2019
1,601
Then increase the length l of the pendulum. The natural period T of a pendulum is given by the equation T=2π√(l/g).
Judging by pictures of your driver mechanism, I think the drive circuit for your pendulum is a variant of this single transistor type. The margin between working efficiently and non-working for that circuit will be narrow. Reducing the swing amplitude significantly would likely reduce the induced pulse to the transistor base and hence stop oscillation.
He said slow down, but I believe he means reduce the amplitude, not the period. His complaint is that the pendulum hits the side, this is not a problem with period.

A mechanical or magnetic solution might be possible, as detailed above.
 
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crutschow

Joined Mar 14, 2008
23,486
Try using a smaller pot in series with the battery, as Dick suggested.
You also might putting one or more small diodes (e.g. 1N4148) in series with the battery.
 
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