Pulse Pendulum Projects

[PhiChaser]

Hi all,

I have been having a lot of fun fooling around with the 'perpendupetulum' (sp?) circuit that TK posted from Nuts and Bolts a couple weeks back. Some of the things I have tried:

I have a coil swinging over a magnet instead of the other way around... I just wanted to prove to myself that it would work either way.

I got a coil and a magnet to swing in opposite directions. Quite difficult to get it to swing exactly the same and required a second magnet on the base (under the swinging coil) pushing against the magnet hanging above the coil enough to just keep it off center. Without the magnet on the base the coil will swing under the suspended magnet. Without a decent way to test, I'm gonna guess that the weight of the magnet vs. the weight of the coil could get both to swing on the same pulse (without the base magnet)? Surely this has been figured out by someone smarter than I already...

I built the circuit on a wooden hobby stick using a button battery and was going to add the spinning 'lid' thing (sort of a TK/lidmotor tribute) but lidmotor totally owned that one so I just have the portable circuit-on-a-stick (ha ha)...

The current build that I have been watching is sort of interesting (to me anyways):
The only way my setup is different than TK's is that the pendulum is hanging about 10cm and so the pulse from the coil only pushes the magnet (and flickers the backwards LED) every other swing.

I have some questions to those of you who know how to actually use your equipment.
What is the best way to hook up a two channel scope to the circuit? In other words: Should I just look at voltage in and voltage out? Across the caps?
What type of waveform would you expect to see?
Does using a rechargeable battery matter to this thing?
Would removing the reversed LED improve the efficiency? Would that little flicker go back into the cap(s) or get lost to the winds? Am I gaining anything out of that flickerless swing?
Maybe I should hook up an old school ammeter on the positive (neg?) leg (in series with the coil) and watch which way the needle swings?
I can't see more than a 0.001V change daily with my cheap DMM so I'm curious how little juice this thing uses...

Put one of these in a small deep picture frame and you have a unique holiday gift! Hiding the coil and adding a Newton's Cradle would be very cool if it could be made to work...

Please feel free to post pulse pendulum pictures.
Thanks in advance for any advice on setup/testing is greatly appreciated.

Peace.
PC

The coil is wound on a regular thread bobbin, 1500 (+/-10) winds of 27?32? Dunno, I don't have any calipers...
The sphere magnet weighs quite a bit more than the coil does and is magnetically suspended from the tip of a square nut from an erector set that is attached to the string.

[dvy1214]

Do alllll that.

Watch the level on the caps vs the level of battery charge to get an idea of the power flow. Try pulsing once for every 2 passes and pulse LED off second pass just to see what happens! Neat little device, don't need to tell you why thats all it is. I'm sure you understand.

[TinselKoala]

Neat!
Scoping very slow circuits like this is kind of a pain, I'd use single-shot trigger mode, and I think you'd see the most interesting information by using the common negative as the reference, and looking at the other side of the coil on one channel and the junction of the resistors and transistor on the other channel.
I'm not quite following your description on the rest of the post, do you mean that with the shorter suspension (mine is 20 cm tall with 10 cm apart at the top) you have such a short period that the cap doesn't charge enough to give you a pulse each passage, so you only get one every other passage?
The LED flicker indicates when a pulse happens, obviously, and you probably have already seen what happens when you have too much supply voltage.
I thought of swinging the coil but never tried it. Have you tried using a photovoltaic cell for the power? And does yours self-start easily?

[PhiChaser]

Neat!
Scoping very slow circuits like this is kind of a pain, I'd use single-shot trigger mode, and I think you'd see the most interesting information by using the common negative as the reference, and looking at the other side of the coil on one channel and the junction of the resistors and transistor on the other channel.
I'm not quite following your description on the rest of the post, do you mean that with the shorter suspension (mine is 20 cm tall with 10 cm apart at the top) you have such a short period that the cap doesn't charge enough to give you a pulse each passage, so you only get one every other passage?
The LED flicker indicates when a pulse happens, obviously, and you probably have already seen what happens when you have too much supply voltage.
I thought of swinging the coil but never tried it. Have you tried using a photovoltaic cell for the power? And does yours self-start easily?

Okay, single shot and common negative as a reference. Thanks!
Yes, exactly right about the shorter suspension (although now mine is shooting off every three out of four passes?)... That makes the most sense why I just see it every other pass; not having enough voltage each time to flicker...
I have not tried a photovoltaic cell for a power source. (I do have one that will work I think, I just haven't tried it yet...)
Every build I have made self starts easily. The coil starts a little slow because it is hanging from it's own supply wires and not thread which gives it a bit of unnecessary friction.
I will try and dig out my scope today and see if I can get some shots of the waveforms...
Thanks again TK!

PC

[PhiChaser]

So I got out my scope and clipped on the probes and had to use the lowest voltage setting on my scope (0.01v/div) with the probes set to 10X to see the waveforms.
I took a bunch of pictures with my tablet but maybe I should have taken a video because my scope DIED... That is to say the power light is still on but nobody is home when I look in the window ya' know?
Ugh...
I opened up 'the box' and this thing was made in 1965...
I hope I live longer than this thing did...

So anyhow, I have four pictures which pretty much sum up what I got to see before the cool moving green lights went out.
-flicker: when the LED was flashing every other swing (only pulsing in one direction)
-noflicker: the magnet swinging over the coil without a flicker
NOTE: the center line is what I set as my top graticule marker for channel 2 on the bottom. Between these two pictures is the typical every other flicker pair.
-flickerflicker: when the LED is flashing every swing of the magnet it looks like the flicker is shorter still (edit: the cap doesn't fill up as far by the looks of it...)
-nonoflicker: when the LED is flashing after 'skipping' a swing; this is where I had a difficult time catching it with the camera on my tablet. I eventually just kept tapping the 'button' until I hit lucky... It looked like the magnet swinging over the coil kept the cap from discharging a second time (when it wanted to) so that it charged up about 1/3 (edit: looks more like 1/2 now that I take another look) of a gridspace more than the flicker trace. Not sure whether the top trace went higher when the cap discharged. Mph...
So what I think I am seeing is the swing of the magnet pushing the voltage down on the capacitor just before it is supposed to discharge? Why is it different sometimes? I'm sure there is a good explanation for it.
Is it more efficient in the hit and miss mode? I have seen it hit three and skip one, hit two and skip three etc... It tends to level out at at every other one (usually heh). Again, I'm sure there are formulae to describe the effects in minutae...
Looks like the LED flashes for a grand total 0.05 seconds? I didn't get a chance to look at the swinging coil or any other builds before my scope died.
Dead scope sucks...

Peace
PC