Novice requiring guidance on creating a XL magnetic pendulum

Thread Starter

bloodshot

Joined May 1, 2020
5
hello

im hoping for some guidance in creating the electronics for a XL pendulum, i bought my mum the toy one on the left and she loved it that much she tried to make a bigger one but it ws made from metal and was to heavy to work, id love to get this complete for her.

1588364640800.png1588364674082.png

untimatly id like this to be battery oporated with a run time of a approx 5-7 hours including 12 leds

iv used this as a guide

this i relize is not going to be powerfull enough to do the job but i puchased anyway

1 mosfet ifzz44n
10 resistors 10k
1 reed switch
10 diode in007
5 capacitor 4700uf, 25v

55kg pull magnet (100mm x 20mm)
550kg N52 magnet (100mm x 20mm)

iv attached image of the sculpture iv created so far the overall weight is approx 4.7kg iv also tried to make a electromagnet out of 500g 0.5 copper
but this does get warm ( no where as near when i connected 2mm copper 500g to 12v car battrey)

FYI i am a novice when it comes to elecronics

thanks in advance
 

MisterBill2

Joined Jan 23, 2018
6,301
Ther arwe multiple ways to drive a pendulum, some much simpler than others and some more effective than others. The purely magnetic ones can either pull it toward the center or toward the ends, or give it a pull as it approaches the center. In addition, if the pendulum is a magnet, then an electromagnet can give it a push.
Sensing can be done inductively or with a photo-electic sensor. So you have a bunch of choices.
The system that I thought was really interesting is one that uses a timer to giv a short magnetic pulse each time as the pendulum approaches the bottom. The fun part of that approach is that the pendulum can just be a steel ball hanging from the ceiling. The challenge is adjusting the timing. But if it has alight that flashes as the magnet is pulsed then setting the time is not so hard. In addition, the circuit is less critical, and the driver can just sit on the floor.
 

Bernard

Joined Aug 7, 2008
5,555
Any idea of how many turns are in your coil ?
Have you mounted a magnet on the end of the pendulum & positioned the coil underneath ?
With a 1.5 V battery you can manually pulse the magnet to find proper polarity to propel the magnet. The eye is a little slow for reliable pulsing so an electronic means is required. The reed switch may work, but I think using the pulse generated by the magnet swinging over the coil would be better. ' Found on the net, Pulse Motors: PerPenduPetulum.
 

MisterBill2

Joined Jan 23, 2018
6,301
Any idea of how many turns are in your coil ?
Have you mounted a magnet on the end of the pendulum & positioned the coil underneath ?
With a 1.5 V battery you can manually pulse the magnet to find proper polarity to propel the magnet. The eye is a little slow for reliable pulsing so an electronic means is required. The reed switch may work, but I think using the pulse generated by the magnet swinging over the coil would be better. ' Found on the net, Pulse Motors: PerPenduPetulum.
The trigger circuit is the reason that I suggested a timer instead.Using the drive coil as a pickup is complicated and probably leads to a greater operating current.
 

Thread Starter

bloodshot

Joined May 1, 2020
5
hi guys thanks for the replys

misterbill- i have started going down the route of the youtube link which is one of the options you mentioned

bernard - unfortunatly i didnt count the turns around when i made it i ended up using a drill, yes i have placed the coil at the base and there is a magnet at the end of the pengalum- when i power it on i do get a good push but it activated on the approch as we as going away so i get a net even and comes to a stop

i need to add a delay when the reed switch is activated and then the coils activates.

im desperately trying to get this swinging by friday as its my mums birthday, i can then work on my utlimate goal on efficient battrey power etc

below is some images of what i did todayWhatsApp Image 2020-05-02 at 20.24.43 (1).jpegWhatsApp Image 2020-05-02 at 20.24.43 (4).jpeg

i tried to use the you tube video as a guide and my understanding was the capacitor created a delay is that correct? do i need a larger capacitor?

when i had it going it would run for 5 - 6 goes and then my power supply would top working and id have to disconnect and wait for it to discharge.

below is my diagram of how i connected it, i got best russlts running a mean well LPV -100 -24 (4.8A)

attempt 1.jpgattempt 2.jpg
 

MisterBill2

Joined Jan 23, 2018
6,301
The capacitor allows a pulse. Current flows in the circuit as the capacitor charges and so if the reed triggers as the magnet approaches then a smaller capacitor will give a shorter pulse. There are two simple options, 1. have the magnet attract as the pendulum approaches, or 2, have the magnet repel as the pendulum passes by. The capacitor sets the pulse width, it does not cause any delay in triggering the pulse.
 

Thread Starter

bloodshot

Joined May 1, 2020
5
im like the coil to repel the magnet just after it passes the coil center,

i have tried it with both repel and attract ( without delay ) and it slows down and stops.

whats the best approach to delay the trigger?
 

MrChips

Joined Oct 2, 2009
21,306
In your photo you show three capacitors connected in series. Is this what you intend to do?
Three 4700μF capacitors in series do not add. They result in a lower value of about 1500μF.
 

atferrari

Joined Jan 6, 2004
4,004
I cannot prove what I am saying here but I guess that something of all this should be displaced whether in time or physically.
 

Thread Starter

bloodshot

Joined May 1, 2020
5
yes the image showed 3 but that was after trying 1 - my incorrect think was it would give a longer delay.

yes timing delay so it doesn't reduce speed on approach and simply keeps pushing it was on each side hopefully to built up height
 

MisterBill2

Joined Jan 23, 2018
6,301
Where is the trigger pickup? If you can move that farther away from the bottom then you can have a short pulse deliver the kick and switch back off before it reaches bottom. And probably a transistor switch will be more efficient than a relay doing the switching. Also, it would use a lower value of capacitor because it needs less input current to switch on.
AND, capacitors in series work like resistors in parallel, so the same formula applies.
 

Bernard

Joined Aug 7, 2008
5,555
If a magnet pole is facing a reed switch, SW, and passes in line with SW the SW will close-open-close, creating a dead zone at center of SW. With a swinging magnet might be best to mount SW at right angle to swing & offset from swing so as not to Passover center of SW. Just another thought- if 2 SWs slightly separated , first SW closes & while still closed second SW closes will give enough inf. to determine direction of swing or when to pulse to repulse. Might use a D FF like 4013, one SW to D, other SW to clock, other ends to gnd. To pulse in both directions, diode OR Q & not Q, differentiate to give a pulse.
Use your FET as coil driver depending on supply V.
 
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MisterBill2

Joined Jan 23, 2018
6,301
How about set the polarity of the magnet and the coil to REPEL the pendulum and the set the switch to trigger dead center on the coil. Suddenly alignment becomes less critical. A push away from the middle is just as good as a pull toward the middle. AND you can get away with a lot more force if you want to.
 

Thread Starter

bloodshot

Joined May 1, 2020
5
If a magnet pole is facing a reed switch, SW, and passes in line with SW the SW will close-open-close, creating a dead zone at center of SW. With a swinging magnet might be best to mount SW at right angle to swing & offset from swing so as not to Passover center of SW. Just another thought- if 2 SWs slightly separated , first SW closes & while still closed second SW closes will give enough inf. to determine direction of swing or when to pulse to repulse. Might use a D FF like 4013, one SW to D, other SW to clock, other ends to gnd. To pulse in both directions, diode OR Q & not Q, differentiate to give a pulse.
Use your FET as coil driver depending on supply V.
ITS ALIVE!!!!!
Your suggestion worked perfectly, by having two SW slightly apart instead of centre it created a delay a type of direction detection and pushes after its gone over the centre very happy man!!

At the moment this is now running on a LED driver
Input - 240v / 2.2a
Output - 24v / 4.2a

Iv looked into power supply and found this
24V 12Ah 25.9V 18650 Li-ion Battery Pack E-Bike , how long would this run it for without the led driver?

Thanks for everyone's input on this! My mum going to be very happy
 

Bernard

Joined Aug 7, 2008
5,555
A pendulum should only need enough power to overcome friction, mW or uW & not Ws.
With 12 LEDs, I might use an AC adapter with 5V @ 100 mA output.
 

MisterBill2

Joined Jan 23, 2018
6,301
I doubt that the coil draws the whole power supply capacity, but even if it does, with the entire pulse sequence running les than a second that will be quite a lot of time. For starters, there are 3600 amp seconds in an amp hour, and so the rated batter capacity is 43, 200 amp seconds. So if the draw is one amp then it will be good for 43,200 swings of the pendulum. at 3 seconds per swing that would be about 130,000 seconds. If my guesses are off a bit, your results may differ
 
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