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need advice for controlling a high amperage solenoid before I complete my parts — Parallax Forums

need advice for controlling a high amperage solenoid before I complete my parts

eagletalontimeagletalontim Posts: 1,399
edited 2009-01-03 05:28 in General Discussion
Well, I am back into some R&D and I need some advice on what parts to order. My new project consists of controlling a solenoid that is mounted to my car. The only problem is that I have to put around 3 amps to it to make it work. It is already grounded so I just need to send power to it. Now....here is the catch..... Depending on a few other factors, the solenoid will sometimes need less than 12 volts. I want to use the PWM command to be able to control this output. My question is, what transistor would I need to be able to handle my application? The solenoid will only be on for 1 second or less so constant strain on the transistor should not be an issue. I was thinking a low speed PNP transistor would work but I am not 100% sure.

One other thing is I want to be able to store about 6 word variables into an eeprom. and ideas on what eeprom to use?

Thanks for the help in advance!

Comments

  • JonnyMacJonnyMac Posts: 9,214
    edited 2009-01-02 21:46
    TIP120 will work (it's actually a Darlington).

    Use a 24LC32 or similar -- it's way bigger than you need but the code you write for it (or download from several examples posted in these forums) will work with bigger EEPROMs in other projects.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2009-01-02 22:33
    ok, thanks [noparse]:)[/noparse] And the development begins!
  • eagletalontimeagletalontim Posts: 1,399
    edited 2009-01-02 22:35
    oh...... isn't the TIP120 a NPN meaning I can only provide a ground to the circuit? I need to be able to control the source voltage.
  • JonnyMacJonnyMac Posts: 9,214
    edited 2009-01-02 22:36
    Well, there's always this crazy new thing called the Internet where one can find data sheets... I'm betting that if one looks one can find a PNP version, like the TIP125 which is included in the TIP120 data sheet (wink).
  • eagletalontimeagletalontim Posts: 1,399
    edited 2009-01-02 22:38
    yep, should have done that first. I do have a tip120 laying around that i bought from radioshack. All it says on the package is that is it is a TIP120 Darlington Transistor. Nothing else. Is that what I am looking for?
  • eagletalontimeagletalontim Posts: 1,399
    edited 2009-01-02 23:18
    ok, since I have a large order on Allelectronics, I was hoping to use one of the eproms they have. Here is the link to what they have to offer. Do you think any of these will be suitable for what I need?

    http://www.allelectronics.com/index.php?page=search&search_query=prom&x=0&y=0

    Thanks!
    Tim
  • Mike GreenMike Green Posts: 23,101
    edited 2009-01-02 23:28
    The 93C46 can be made to work. It's a 128 byte EEPROM (see www.atmel.com/dyn/resources/prod_documents/doc0172.pdf).

    It uses SPI mode and would use the SHIFTOUT and SHIFTIN statements for the clock (SK) and data (DI / DO) lines and HIGH / LOW for the chip select (CS) line.

    I don't know if you will find any examples of its use. There are other types of EEPROMs with lots of examples of Stamp code, but not any on the Allelectronics page you showed. JonnyMac is right. Stick with EEPROMs that are easy to use like the 24LC32 or larger.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2009-01-02 23:32
    ok, i would rather stay with something someone on here knows about instead of waisting money tongue.gif
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-01-03 00:15
    eagletalontim,

    Remember that a Darlington will drop 1.2Volts across the Emitter-Collector junction... At 3 Amps that's 3.6 Watts of heat you will need to dissipate. I would also look into P-Channel Mosfets for this application.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2009-01-03 00:24
    well, the original circuit that was on the car has a to-220 transistor that runs the solenoid, but i have no idea what it is. all it has on it is T 3595 2b I searched for that on google and did not come up with a match or another component that will work in it's place.
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-01-03 05:28
    Look at this web page and see if can out how made the transistor


    http://www.classiccmp.org/rtellason/logos/semiconductorlogos.html

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them

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    Sam
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