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555 Timers
Forum Bounce Servo with 555 timer
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Related

Bounce Servo with 555 timer

Eric
Eric over 3 years ago

I want to toggle a servo with the push(and release) of a button.  I then want the servo to return to original position after x seconds.  I think I'm close by enlisting a 555 timer.  I have it successfully powering an LED for 1 second. (hold your applause)

Is this at least possible with this same circuit?  This is just a hobby project and I was trying to avoid grabbing an Arduino and coding something.

When I tried to connect my servo to pin 3, positive, and negative....it moved slightly once out of 10 attempts.  The LED is dimmer and shorter lived while the servo is attached.  

I should check back in here at least once a day until I get this working (and will report so) or smash the thing with a bat.

-EP

Some details...may be garbage.  THANKS IN ADVANCE!

Power = old 9v battery (8v)
Resistors = 10k
Cap = 100uf

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  • jc2048
    jc2048 over 3 years ago +4 verified
    Does this do what you wanted (sorry the video is a bit blurry)? community.element14.com/.../7411.MVI_5F00_3478.MOV Here's the circuit and the build on a breadboard the start position is controlled…
  • scottiebabe
    scottiebabe over 3 years ago in reply to jc2048 +3
    Neat little circuit. I wonder if I can upload .asc files on the new website. In the holiday spirit I put JC2048's deign into LTSpice for one to experiment with too. community.element14.com/.../1641.JC2048Servo…
  • dougw
    dougw over 3 years ago +2
    As @ scottiebabe points out it is a bit tricky but possible to do with 555 timers. You could make the middle waveform with a 556 (dual 555) - one 555 would generate a continuous square wave with 20 ms…
Parents
  • jc2048
    +1 jc2048 over 3 years ago

    Does this do what you wanted (sorry the video is a bit blurry)?

    Video processing failed.
    You don't have permission to edit metadata of this video.

    Here's the circuit and the build on a breadboard

    image

    image


    the start position is controlled by the 1k resistor under the 1N4148, the end position by the 470n capacitor
    controlled by the MOSFET (I actually used two 470n in parallel, so the circuit value's wrong), and the delay time
    after the switch is released is set by the 150k and the 10u.

    These are the output waveforms going to the servo, in case you're interested. First is the rest position, the second
    the position when the switch is pressed.

    image

    image

    Anyway, it will give you something to play with if you're interested in experimenting with a 555.

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  • Eric
    0 Eric over 3 years ago in reply to jc2048

    So, full disclosure, I inherited several pounds of components and am just getting my feet wet.  I think I saw some of those orange\black (diode?) pieces.  And I think another video labeled that  black 'D' shape a transistor.(EDIT: that is the mosfet. I had only seen them as rectangles)  I'll have to search for any mosfets.  I don't have a fancy power supply(yet) that I can dial in the voltage...so I'm just playing on a worn out 9v.  I think some math still works as I saw the 555 timer works with fractions of the power (1/3, 2/3).  THANKS for understanding my request!  Seems like this is an answer, but I want to attempt it first.  My personal attempt didn't go great, but I feel this is a working solution and have marked it as such. Thanks for all the quick replies and interest!

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  • jc2048
    0 jc2048 over 3 years ago in reply to Eric

    A worn out 9V battery won't work too well with a servo. You'd do better with 4 fresh AA batteries for a fairly robust 6V. A low cost way to get the battery holder might be to look for an old consumer device and use the battery compartment (an old wrecked toy or radio, or something like that).

    Almost any small n-channel MOSFET would work here. I used the BS170 because I had some, but mentioned the 2N7000 because they're more common and people are more likely to have them. For the connections, look in the datasheet. Beware, though: the connections vary, so you do need to look them up - don't assume they're all the same. Here are the pinouts for the BS170 and 2N7000 and you can see that they're different.

    image

    image


    The circuit isn't very precise and the timing will vary as the supply voltage changes. I haven't helped by putting in the diodes to separate the charge and discharge path to get a short pulse time. For the diodes, 1N914 are common too and you may have some of those.

    You can extend the delay time by increasing either the 150k or the 10u next to it. If you go too far though, the return of the servo at the end will get more and more sluggish.

    One small problem with a servo is that it has a motor and can produce lots of electrical noise. That might affect the timing circuit. If you have any doubts, run the servo on a different supply (with the grounds still connected together) and see if that cures it. If it does, you'll need to clean up the supply to the timing circuit.

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  • jc2048
    0 jc2048 over 3 years ago in reply to Eric

    A worn out 9V battery won't work too well with a servo. You'd do better with 4 fresh AA batteries for a fairly robust 6V. A low cost way to get the battery holder might be to look for an old consumer device and use the battery compartment (an old wrecked toy or radio, or something like that).

    Almost any small n-channel MOSFET would work here. I used the BS170 because I had some, but mentioned the 2N7000 because they're more common and people are more likely to have them. For the connections, look in the datasheet. Beware, though: the connections vary, so you do need to look them up - don't assume they're all the same. Here are the pinouts for the BS170 and 2N7000 and you can see that they're different.

    image

    image


    The circuit isn't very precise and the timing will vary as the supply voltage changes. I haven't helped by putting in the diodes to separate the charge and discharge path to get a short pulse time. For the diodes, 1N914 are common too and you may have some of those.

    You can extend the delay time by increasing either the 150k or the 10u next to it. If you go too far though, the return of the servo at the end will get more and more sluggish.

    One small problem with a servo is that it has a motor and can produce lots of electrical noise. That might affect the timing circuit. If you have any doubts, run the servo on a different supply (with the grounds still connected together) and see if that cures it. If it does, you'll need to clean up the supply to the timing circuit.

    • Cancel
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