Bedini Schoolgirl

[ren]

Hello everyone. I have recently began replications of various pulse motors, on top of learning electronics from scratch. I took particular interest in the sony reel to reel that Aaron(?) modified for 10000 rpm. What fascinated me was the amp draw dropping at higher speed. I have made a simple bedini circuit 3 air coil pulse motor with a hard drive bearing and platter for a rotor. Neos alternating north and south 8 in total. Draws just over .5 amps at FAST speeds. Can recharge 9v alakalines (non rechargeables) without heating them. Coils run dead cold.

It has (along with Aarons jet engine) inspired me to go on, and continue replications. I will post up some pics and video/schematics soon.

Look forward to following this thread and hearing everyones input.


S

PS old reels out of vcr machines have excellent bearings too. There are even all mounting holes pre-drilled to attach to frame and rotor. Should be easy to find with dvds flooding the market.

[ERKAN]

Ne-2

Does anybody knows where I can buy this neon bulb? I couldn't find it in Radio Shack and on the internet everybody is seling 120V ones.
Thanks,
Erkan

[Jetijs]

I got mine from ebay. Just searched for them again and found 4 sellers that sell them.

[ren]

jaycar in australia have them. Ebay, or any electrical component site will hook you up

[gabriolaman]

hi guys im newish here and im starting to collect the parts i need and im wondering where i might canabilize the transistor as theres no electronics parts stores near me what kind of stats does the transistor need besides voltage and currect requirments if i were to use one unspecified thanks for any help

[Jan H]

Gabriolaman,

anyone on the forum please correct me if im wrong.
I think the transistors used in the schoolgirl circuit are pretty close to the end-amps in conventional Audio amplifiers. But that is not saying every audio amp has the right parts. Especially cheap low power systems have these all-in-one piecies of junk wich are just of no use at all. I think you will have to look at bigger, stand alone amplifiers.
Pretty much expensive machines to destroy for a 2 dollar part.
you'd better try online stores.

[gabriolaman]

ok ile try get one i been testing differnt npn transistorsand so far i can get them to blink a l.e.d but they wont power my electromagnet i can get my hands on a blown car audio sub amp maybe ile find one in there thanks for your reply

[Peter Lindemann]

120 Volt Neon Bulbs

Does anybody knows where I can buy this neon bulb? I couldn't find it in Radio Shack and on the internet everybody is selling 120V ones.
Thanks,
Erkan

Erkan,

The 120 volt Neon Bulbs will work. They are usually in a little plastic case (red, green, or yellow). Just open up the plastic case. You will see the neon bulb connected to a SERIES RESISTOR. Just remove the resistor and like magic you have a neon bulb.

So, you can get a neon bulb easily. Next, you will notice that the little ones can't handle much current, so be careful. Remember, the neon bulb is a "safety relief valve" to protect the transistor in-case the circuit is mistakenly operated without a load to receive the inductive collapse.

Peter

[ren]

Peter, or anyone, would two bulbs across collector and emitter offer better protection? I seem to have burnt out a couple in my experimenting....

[hydrymoron]

SG diode query

Hullo everyone. I'm tying to put together my first SG, and I have a couple of questions to put to wiser heads.
1. I am currently trying a 1N4004 diode, which was the nearest the shop had to the 1N4001 recommended. The only difference seems to be in the voltage rating (400 instead of 100). Would this do the job? I also have some 1N4007s available.
2.I couldn't get a neon bulb so I tried using a low Ma incandescent bulb. Is this any good or would I do better leaving it out altogether? (I have it in series between the diode and the emitter, as shown in one of the diagrams).
3. I'm using four small 1cm diam. neodynium disk magnets. I'm a bit confused here because some people seem to recommend them while others say you should only use ceramic magnets.

As you've probably guessed, the circuit doesn't seem to work. I've checked the usual things, coil direction (about 400 winds) showing north to magnets' north. Without the core, the coil sometimes emits an oscillating whine which increases in pitch. Does this mean anything good or bad? When a clip slipped and briefly shorted the emitter to the casing I think I saw the rotor move slightly. When I connect and disconnect the circuit, I can hear a faint clicking sound coming from the rotor (based on a HD drive so quite free running).
Any suggestions would be gratefully received.

[Jetijs]

1. Yes you can use the 1N4004 diode.
2. incandescent bulb wont work at all and is the reason that your circuit is not working, because neon turns on only at about 90V, but incandescent bulb is always on. Have you seen how the neon bulb looks like? There is two seperated electrodes in a glass envelope and the electrodes are not touching, the bulb does not conduct electricity. But when we apply 90V to the bulb, the gass between the electrodes starts to ionize and conduct electricity. Your incandescent bulb conducts always and that is not good. If you do not have a neon bulb, then just leave it out, but in that case be careful not to rotate the wheel while the charging battery is not connected. I have used my ssg many times without a neon bulb - works fine, as long as your charging battery is attached. The neon only protects the transistor in case there is nothing connected in the outpus (charging battery) and the radiant spike has nowhere to go, so it overshoots through the neon to the primary battery negative terminal.
3. You can use neo magnets, but they are not recommended, because they are too strong and can saturate and permanently magnetize your core material, that is bad


Hope this helps

[Jetijs]

Peter, or anyone, would two bulbs across collector and emitter offer better protection? I seem to have burnt out a couple in my experimenting....

I dont think, that 2 bulbs in parralel will provide better protection. You could try using a 4.7k 1-2w resistor in series with the neon. This is what Rick did and it seems work better.

[hydrymoron]

Re. Diode query

Thanks for that Jetijs. I took out the bulb but still no joy. One thing I noticed is that although the coil seems to be working right, when I use a compass to check it, the response is very feeble, with the needle looking as if it isn't sure if it doesn't prefer the earths magnetic field to my coil. When winding the coil I did my best to follow the instructions (up and over, left to right and then back) but although I did my best to keep the two strands together, it proved very difficult and there may have been a few gaps here and there.
The core is a piece of iron (cast, I think) I found lying around, but it's a bit of a loose fit. I tried with a steel bolt, but no difference.
Would it be worth rewinding, this time with twisted pairs, or is it just that 400 turns is not enough. If I need to add more, what's the procedure for connecting extra coil wire?
Thanks again.

[Jetijs]

I do not think, that the problem is in the coil. 400 turns should work just fine. Can you post some pictures of your setup? Check if all components are working and if everything is wired exactly as in the diagramm. Maybe your transistor is fried, maybe something else. Hard to say

[hydrymoron]

Re. Diode query

Here are the pics. I've resoldered and rechecked everything. One thing I notice is when I put a meter across the 10 ohm resistance (negative probe towards the transistor only) the coil begins to oscillate and the rotor tries to turn.