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Pneumatics @ 24V stamp at 5V. How to interface? — Parallax Forums

Pneumatics @ 24V stamp at 5V. How to interface?

elliottelliott Posts: 14
edited 2005-08-16 03:09 in Robotics
Hello Thanks for the input -

I'm working on a Midi based robotic drum kit. It uses pneumatic cylinders to strike the drum heads. Stamps (andPICS) run at +5Volts. The Solenoids that I'm trying to interface with are really just simple switches, However they run at 24Volts. Is there a simple way to connect to them? jumpin.gif

Comments

  • dandreaedandreae Posts: 1,375
    edited 2005-08-14 18:04
    Check out the Nuts&Volts article number 6 at this link:· http://www.parallax.com/detail.asp?product_id=500-00005

    Dave

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    Dave Andreae

    Tech Support
    dandreae@parallax.com
    Http://www.parallax.com

    ·
  • elliottelliott Posts: 14
    edited 2005-08-14 19:24
    Dave-

    wow thanks for the comprehensive reply! THis is super helpful!!!

    one last question on the ULN2003's... will they handle 24VOLTS? the data sheet lists the Vo= 50 and the Vi as 30. This means that i can use this safely to run the INs at +5volts and the "other side" the outs and "supply" at 24 volts correct?

    that would be fantastic and so simple....


    thanks in advance

    elliott hop.gif
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-14 19:58
    elliott,

    ·· What is the current rating of the 24V devices you mentioned?

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  • elliottelliott Posts: 14
    edited 2005-08-14 20:45
    Hey-

    the solenoids (8 of them) are rated: Valve coils are rated 24 VDC 6 watts each


    elliott
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-14 23:16
    elliott,

    ·· That means that they draw approximately 250mA.· I would estimate high.· The ULN can handle up to 500mA per output, but not all driven at the same time.· How many do you expect to have going at once, and what is the estimated duty cycle?

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  • elliottelliott Posts: 14
    edited 2005-08-14 23:32
    it is for a drum kit. So each solenoid will fire for approximately .25 to 1 sec. Rapid firing of some of the solenoids is desirable. In some drum patterns, the kick drum and the High hat, or the kick drum and the snare will strie at the same time. Additionally, there are tiems when the solenoid controlling the high hat's foot pedal will stay "depressed" (on) while the rest of the pattern plays. However because speed and percussiveness is the order of the day, the solenoids (other than the hi hat foot pedal) will fire as briefly as possible hopefully in the order of 250 milliseconds
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-15 00:01
    elliott,

    ·· It could work.· In a few areas it seems a little close on current tolerances, but you can always test actual current draw before committing to anything.· I would definately test the solenoids current draw instead of basing things on the Power/Voltage calculation.


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    Post Edited (Chris Savage (Parallax)) : 8/15/2005 2:45:43 PM GMT
  • elliottelliott Posts: 14
    edited 2005-08-15 12:48
    idea.gif

    first of all SINCERE THANKS FOR all the help with this issue!!! On digikey's site I found a Darlington chip thats rated to 1.5 amps. Would this solve the problem?


    ULN2067B IC SWITCH QUAD DARL 16 POWERDIP STMicroelectronics

    NPN - Darlington
    50V
    1.5A
    4 Darlington
    16-DIP


    DIGIKEY PART# 497-2350-5-ND
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-15 14:56
    Hmmm,

    ·· Oddly the chip would seem to have a robust darlington system, but yet the max power dissapation is listed at a mere 4.3W.· Your solenoids draw 6W each.· I'd have to look into it more.

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  • ManuelManuel Posts: 105
    edited 2005-08-15 20:25
    Hello
    How much did your solenoids cost u and·can you control the presure or are they just on/off?


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    Best Regards

    Manuel C. Reinhard
  • elliottelliott Posts: 14
    edited 2005-08-16 03:09
    jumpin.gif
    my solenoids were an absolute steal. they're from CandH sales. They sell used equipment. There are eight solenoids coupled to a distribution manifold, with a 60 psi regulator included. I'm currently workin gon Version 2.0 of the drum kit. In the first version, I bought all of the solenoids and valves from Mcmaster carr. The valves were 25 bucks a pop. the Solenoids were similar. the manifold was like 90 bucks and on and on... and no they are simple on and off solenoids. The "velocity" sensitive do exist, however in my research I have only found them new for over $400 each.

    From my perspective there are enough engineering challenges with just the stick mechanism. I eventually want to find some used velocity sensitive solenoids. but given that this is my second attempt at creating a the kit I realize that this is a very long term process.
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