Help with electric cat

"Pokey" schrieb im Newsbeitrag news: snipped-for-privacy@51g2000cwl.googlegroups.com... | Would you please help me fix my electric cat? I've spent hours | screwing around with it. Let's start with something you guys love, an | ASCII drawing! | | N/C | E | \\| + | |-B----o-------(|--------o N/C | C /| Q1 | C2 | o | | | | + | | o-------(|--------o | | | C1 | | | | _____ | | | o----|_____|------o | | R1 | | | | | | | | o------------o--o|o--o-----o | o|o | o|o L1 | o--o|o--o | | | | o-------o | | Two of the leads are tied together | | | Notes: | | This circuit powers my electric cat. They said the would replace it | but I'd have to send it all the way back to China. How hard can it be | to repair an electric cat of five parts? Nuts! The paw is nothing but | a pendulum with a strong magnet on it. I think the capacitors charge | up from the single AA battery in the circuit and alternatively dump | their voltage to the coil which then influences the magnet. I'm | guessing the coil is two coils wrapped in one since it has four wires? | Not sure. The coil is the size of a quarter and about 1/4 inch tall. | | The circuit has horrible chinese solder. It has the thinest wires I've | even seen that go to the single AA battery that powers it. When I | opened the case, the wires snapped right off so I'm unsure where to | connect them. The emitter of Q1 is floating, that is, not connected to | anything else in circuit so I tried connecting +1.5V to it but no luck. | My guess was +1.5V to E of Q1, and ground to common of L1 (where they | are tied together) or C2 where it is N/C. It doesn't seem to work. I | tried some other combinations but no luck. I tested Q1 in circuit with | my DMM so it is not shorted. I've screwed around for hours with this | thing! | | Q1 = S9014 NPN, with emitter on vacation | C1 = 47uf 16v | C2 = 47uf 50v | R1 = 120k | L1 = Coil, copper wound value unknown measured 300 ohm in circuit. | | Questions: | | 1. Can you tell me what to to connect the leads from the single AA | battery to rather than me continuing to guess? | 2. Can you explain how the circuit works? Since Q1 is an NPN, when the | base is .7V more than the emitter voltage, the emitter is then | "connected" to the collector. However the emitter in this circuit is | not connected to anything so that doesn't make sense. | 3. Can I substitute a 2N3904 for the S9014 NPN transistor assuming it's | bad?

Where is the battery and load connected? If your schematic is correct then Q1 is working as a diode.

- Henry

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is working as a diode.

Hi Henry,

Sadly the wires snapped off when I opened the cat so I don't know where the 1.5V DC load gets connected. The quality of the solder and wires is very poor.

Shall I place another order with the communists assuming this high tech cat is outside the limits of the knowledge of democratic nations?

We have very little to go by here - there are a couple of possibilities for your circuit, but we'd be guessing.

Can you post a decent photo of what you have now?

Thanks, Rich

Yes I'm afraid I was guessing a lot myself.

Not sure if it will help but here are some pics:

I did a simulation on the circuit as modified above, and it will oscillate at about 2 cycles per second if L1 is a 40 Henry center tapped coil. This is essentially a Hartley Oscillator, and it has a good sine wave. I assume there is an iron slug in the coil mechanically attached to the tail. This complicates the simulation because the inductance increases as the slug of the solenoid pulls in.

There are other possibilities if there is a switch hidden inside the coil. Or maybe it needs some Electric Catnip to wake it from its Electric Catnap? :)

I can email the LTSpice file if you want to play with it. Or cut and paste the ASCII data following:

Paul

Version 4 SHEET 1 880 680 WIRE -16 16 -176 16 WIRE 336 16 -16 16 WIRE 144 80 -96 80 WIRE 240 80 144 80 WIRE 336 96 336 16 WIRE -16 128 -16 16 WIRE 144 160 64 160 WIRE 240 176 240 80 WIRE 336 176 240 176 WIRE -96 208 -96 80 WIRE 144 208 144 160 WIRE -16 224 -16 192 WIRE 64 224 64 160 WIRE 64 224 -16 224 WIRE 144 224 144 208 WIRE 48 272 -16 272 WIRE 80 272 48 272 WIRE -16 304 -16 272 WIRE 48 320 48 272 WIRE -176 416 -176 16 WIRE -16 416 -16 384 WIRE -16 416 -176 416 WIRE 48 416 48 384 WIRE 48 416 -16 416 WIRE -96 448 -96 288 WIRE 144 448 144 320 WIRE 144 448 -96 448 FLAG -96 448 0 FLAG 144 208 Vout SYMBOL voltage -96 192 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 1.5 SYMBOL npn 80 224 R0 SYMATTR InstName Q1 SYMATTR Value 2N2219A SYMBOL res -32 288 R0 SYMATTR InstName R1 SYMATTR Value 120k SYMBOL cap -32 128 R0 SYMATTR InstName C1 SYMATTR Value 47µ SYMBOL cap 32 320 R0 SYMATTR InstName C2 SYMATTR Value 47µ SYMBOL ind2 128 64 R0 SYMATTR InstName L1 SYMATTR Value 20 SYMATTR Type ind SYMBOL ind2 320 80 R0 SYMATTR InstName L2 SYMATTR Value 20 SYMATTR Type ind TEXT -130 506 Left 0 !.tran 5s startup\\nK1 L1 L2 1

Similar circuits existed in the first electronic clocks. Effectively a normal pendulum clock mechanism (with an attached magnet) driven by a one-transistor oscillator. Like the one above.

The pendulum (cat paw) and attached magnet has it's own resonant frequency to which the oscillator locks. If your simulation gave 2Hz, you're probably close. The slug/magnet will increase the inductance a bit on average and the paw will probably oscillate at 1 Hz or so.

The point is, this is not a simple inductor/transformer. There is some energy exchanged (inductively) with the pendulum, which is an oscillator itself. The circuit may not even oscillate on its own, in which case you need to start the pendulum manually.

If the OP wires his circuit like you did and hasn't fried the transistor (any small-signal type should work) the cat is back in business. :-)

Regards,

Iwo

Thanks! I'll give it a go.