555 Two-fer – Baby Swing Upgrade And A Headphone Tube Amp


[Jason] sent in two 555 timer driven items that were worth sharing, both of which are entries in the 555 Design Contest.

The first item is a circuit that automatically resets an infant swing. [Jay], who built both items, has an infant swing for his daughter that spins a mobile and plays music. It’s great but it only works for 7 minutes and 15 seconds before a button push is required to trigger it again. He found this limitation to be annoying, and as I have owned the same swing, I can echo his frustrations. He probed the swing and found that a 5v pulse was required to reactivate the mobile, but it had to be sent after it turned off to have any effect. He put together a simple circuit that would do the button pushing for him, as you can see in the video below.

[Jay’s] other entry is a headphone tube amp using a quartet of 6DJ8 vacuum tubes. The 555 timer in the amp is used to drive a FET and the hand-wound transformer he built for the amp. You can see a video of the amp in action below as well.

The projects are lacking a thorough write-up, but he does provide schematics for both the swing reset switch and the tube amp for those looking to replicate either item.



22 thoughts on “555 Two-fer – Baby Swing Upgrade And A Headphone Tube Amp

  1. OK, the second one is kinda cool, but i’ve done the swing hack using nothing more than a switch, a capacitor, and a normally closed relay.

    Connect a capacitor on the motor line to provide a constant signal when the motor is running. Connect this to the switching leg of the relay. Add a few diodes at the cap if the motor on yours is impelling both ways.

    This way whenever the motor is running, the relay is open, and as soon as the motor cuts off the capacitor discharges completely and the relay snaps closed.

    Add your switch just before the switching arm of the relay, and the whole thing will operate unattended for as long as you like.

    1. I would have done it with a toggle switch but this was for the 555 contest. A relay in my opinion is overkill, but to each his own. That is the beauty of electronics, there are 1000 ways to skin a cat.

  2. @Elias – You may have noticed Mike posting about the 555 Contest that’s going on currently… along with all of those 555 circuits. See the link in his post ;-) I agree the 555 is not the best choice always, but it is a very commonly available part that is quite versatile.

  3. @jason How exactly would you wire up a toggle switch to push a button after something turns off?

    This is an honest question btw, I’m not trying to be facetious.

    Also, just in case we’re talking about a different type of toggle, locally a toggle switch refers to a simple on/off spst toggle…

  4. @eldorel:
    The toggle switch(SPST) would be wired in parallel with the reset button. This is basically how my 555 drives the circuit. the vcc of my circuit is on the “HOT” side of the switch(the +5v), and the output from pin 3 of the 555 goes to a mmbt4403 PNP transistor via a 10k resistor to the base. the emitter is also tied to the “hot” side of the reset switch. the collector is then going to the other side of the reset switch. I hope this has cleared things up for you. It is sort of silly to infer that i would somehow use a toggle switch to “push” a button.

  5. @Macw – Wow, you obviously don’t have kids and don’t know what the hell you are talking about. Babies don’t fall asleep in 7 minutes, and if the lights and sounds stops before that happens… you start the process of dozing off all over again. Maybe you should worry a little less about trolling, and a little more about hacking.

  6. We have the same swing. Its great and the babies love it but Im sure its set to 7minutes to annoy parents. As soon as either of the girls start dozing it stops. It works wonders when they are teething too, keeps them relaxed.

    Although on the first day I had to make a quick mod to fit a DC socket to power it from a PS2 Slim power supply instead of D Cells that last about an hour.

  7. @macw – Yep, it is absolutely neglect when you are 10 feet away and can see the baby. Clearly you haven’t had kids yet, or you are a “helicopter parent”. Either way, there is nothing more interruptive than getting up during dinner every 7 minutes to re-trigger a mobile for a fussy baby who is just on the verge of sleep. That goes for the parents as well as the baby trying to make her way to dreamland.

    @hc – Sure that’s an option, but it seems a bit inelegant, doesn’t it? I can hold both the brake and gas while sitting at a stop light, with the knowledge that at some point I can let go of the brake. That’s just silly though.

  8. @phillip:

    Its funny that you mention a wall adapter…I did that the first week after the D batteries died as well. I glad there are people out there who understand that as you are sitting just out of arm’s reach of the darned button the swing stops you don’t want to keep leaning over to push it. This has been the most annoying thing. If anyone is interested i can take pictures of the places on the board that i attached my circuit…BTW thanks to everyone for dealing with the trolls….

  9. Okay, let’s see.. trolling comments: Check! Inane comments: Check! Racist comment: Check! I’m-way-better-than-you-cuz-I’d-have-done-it-this-way-even-though-my-last-electronics-project-was-when-I-used-two-“C”-cells-in-place-of-“Ds” comment: Check! One serious and on topic comment: Check!
    Must be the Hackaday Comment section! I vote for the disabling of the Hackaday Comment section. Seconders?

  10. @bryon,
    thats not just the hackaday comments. thats 99% of comments on the internet. ill also put a nah to your question regarding the closure of comments. iv learned to much from them. if you dont like then then just dont read them. simple eh? freedom of speech FTW!! btw, they do eat cats in china, mainly the Cantonese, but still in china so no racism yet.

  11. @Bryon – the comments are the best part! Where would all the 555 Trolls, and Arduino Nazi’s go if comments were disabled??? I guess I’m half kidding… anyhoo, nice of you to paraphrase the crazy ass comments above, I got a chuckle out of it.

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