Cradle Swing Motor Controller Modification (Vid Added)
- March 9th, 2011
- Posted in 555 Timer . Electronics
- By Jay(Gresko Industries)
- Write comment
This swing has had a rough life. Last week the controls finally had enough, and burned up completely. This left me with a swing that doesn’t rock. On it’s way out it left me a parting gift, it shorted out my new motor…Sigh. So now i have set out to “Make it right” and make my own PWM motor controller. It only took 2 days to design, prototype, and build this little gem. I will have to say that the Rigol scope i bought was the best investment EVER! It’s so easy to use and helps you see what you need, when you need it. I got the parts home and prototyped it, perfect! Now that it works lets make it permanent. I have a few pictures but i will have to upload them later. Needless to say, the cradle is swinging again! My baby is happy once again. Brett did some exploratory surgery on his swing and also came up with how the swing originally operated. I encourage him to edit this post with his videos and information. he has some good screenshots of the output waveforms and such of his swing.
Schematic: Cradle Swing Motor Controller (293)
Cradle Swing Reverse Engineering:
The Original circuit had a signal diode (1N4001) and a 1micro farad cap in parallel, across the motor, (chassis grounded). This would probably explain why you fried your motor. The back initial strain and back EMF would have been taken care of by this simple configuration.
Hi Bob, thanks for the comments, but your assumption is incorrect. I agree leaving the diode off would be bad (cap not so much), but applying 6 volts to a 3 volt motor would also be, but the diode/cap was in fact transferred to the new motor. In this failure case even more voltage was applied, through a laptop power supply by mistake… read here:
http://fightcube.hackhut.com/2011/02/25/cradle-swing-repair/
Brett (and Jay if you read this),
I have a very similar swing and I recently added a 6V AC transformer so I can plug it in, also I added an audio input to the speaker so I could hook up an mp3 player (the original sounds never worked.) Now the motor seems to be on it’s way out. I read the original hack and was thinking of using the air freshener motor as a replacement. But from this comment it seems like it might be a bad idea. It looks like the air freshener motor runs on 2 AA, making it a 3 volt, and here you say 6V through a 3V is bad. Could you clarify a bit for me? Do you now think that the motor that was swapped was the wrong voltage?
Thanks,
John
p.s. here’s a link to what I’ve done so far: http://www.youtube.com/watch?v=wK1t2Fwu7hk&feature=player_detailpage
Hi John,
The voltage rating on the motor is a little misleading. The way the Fisher Price circuit works, they PWM the motor using 6V, but never go higher than 50% PWM. So the average motor voltage is 3V max. Hope that helps alleviate your concerns about the replacement motor. Don’t forget your clamp diode. Jay can tell you more about this since he’s been selling replacement motors on eBay.
Hey,
I hope you didn’t put 6v AC to the swing, otherwise R.I.P…6V DC on the other hand is OK, for swings that take 4 C batteries like mine did. The motor can handle 3 v nominal, which is what the controller is providing through PWM. If you motor is dying and you can’t find an air freshener i sell them on ebay. good luck.
Bob,
If you read the original article you would have seen that the reason it burned up was because 16v was applied to the controller, not my incompetence as an technician/engineer. It’s kinda lame to come off like you know what happened when you weren’t even there. Thanks for the comments though…