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  1. #1
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    Solenoid for Z probing

    I am trying to use a solenoid instead of a proximity sensor to probe the bed, since the proximity sensor is heat sensitive and gives different results based on temp. The solenoid is connected to Pin5 and 2 on the PWM above the Mega chip.
    I chanded the FW and when I send a M402 i only read 4.77v. Since my solenoid is 5v it is not enough to trigger it and I thought I should have 12v on that pin 5 anyway. Any ideas?

  2. #2
    Super Moderator Roxy's Avatar
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    Can you post some pictures of the probe engaged and retracted? Did you do anything to handle the inductive kick when the power cycles off to the solenoid? And... If it is a solenoid, why do you need to use the PWM mode of the output pins? Wouldn't just on or off make sense?

  3. #3
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    Quote Originally Posted by Roxy View Post
    Can you post some pictures of the probe engaged and retracted? Did you do anything to handle the inductive kick when the power cycles off to the solenoid? And... If it is a solenoid, why do you need to use the PWM mode of the output pins? Wouldn't just on or off make sense?
    http://cdn.sparkfun.com/datasheets/R...s/ZHO-420S.pdf
    This is the solenoid, yes on/off would be good enough, thought that is what I am doing. Got only e1 out left. That is why I thought about pin 5


    Can't upload pics, it's not working
    Last edited by Fri; 04-26-2015 at 12:56 PM.

  4. #4
    Super Moderator Roxy's Avatar
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    OK... Do you understand why I was questioning if PWM (Pulse Width Modulation) made sense? That kind of feels like a bad thing to do with a solenoid.

  5. #5
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    Good, thanks, where could I attache that solenoid right now I am working on a ramps board, which out would you use to turn it on when z probing?

  6. #6
    Super Moderator Roxy's Avatar
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    Well... I don't know off the top of my head. I would have to have schematics and more details from you. But here is what I can tell you off the top of my head. Most (if not all???) of the GPIO (General Purpose Input Output) pins can be configured as input or output. The pins that can do PWM are most likely not GPIO pins. They are even more flexible than GPIO pins. My guess is they can be configured to be just plain, stupid, simple Input or Output. If so... You can just use the same pin in a crippled mode.

    But otherwise, you should be able to connect to some other GPIO pin and say it is output, and just set it high or low as needed.
    Last edited by Roxy; 04-26-2015 at 03:09 PM.

  7. #7
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    Okay, some other people have done this and refer to the output as ramps digital output and assign pin 63.

  8. #8
    Super Moderator Roxy's Avatar
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    Do you have a reverse biased diode across the solenoid? If this question doesn't make sense to you, please say so! It is very possible to fry your electronics doing this kind of stuff if you don't account for the inductive kick.

  9. #9
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    No right now I am just trying to find a 12v out that will react to the M401 with pin64 for z probe, the solenoid is not connected, but also, no this doesn't make sense to me. I am just trying to follow this http://community.robo3d.com/index.ph...stock-r1.3864/

  10. #10
    Super Moderator Roxy's Avatar
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    This circuit does have a reverse biased diode across its solenoid! If you follow its directions you will not cook your electronics.

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