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Noob joining

MazdaMazda Posts: 5
edited 2006-04-04 00:18 in BASIC Stamp
Hi all,
I just bought a stamp, and I'm ready to start playing devil.gif

I'm pretty new to embedded controllers, but I program for a living, so hopefully· that will help with something.· Anyway, I learn best by trying to build something, so I figured I might as well make something I can use in my car project.

I'm in the middle of upgrading a kit car, and would like to use the stamp to perform various functions involving dash button operation, theft prevention and a basic display.

In short, I'll be :

reading a· tach signal, and various button activities,
controlling·up to 4 automotive relays,
displaying some stuff on a small LCD display,
and using a RFID tag.

There is a wealth of information here and generally on the web, so I've been doing a little reading on what I need.· Can someone tell me if I'm on the right path?

For driving the relays, I was thinking about using a H11B1 opto.· From what I saw, the only thing I need on that is a 330 ohm resistor on the +5 input line.

For reading the tach, could I use a 4N25 opto?· The source of the tach is a GM PCM tach output line.

For the rocker switches, all I need a pull down resistor, right?· Debounce through software?

The RFID and LCD should be direct hookups with no other components needed?

For power supply, would a LM7805 and a 220 microF capacitor be sufficient?

Thanks for the help.

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-04-03 18:37
    Hello,

    ·· Most of your connections sound right, except the Relay Driver.· I am not familiar with the· opto part # you mentioned, but the device driving the relay should be able to handle the current and back EMF from the device.· I have never seen an opto that could do this.· Here is an example Relay circuit we have.



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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
    Relay Driver.jpg
    420 x 402 - 20K
  • MazdaMazda Posts: 5
    edited 2006-04-03 18:43
    Hi Chris, thanks for the quick reply.

    This is where I saw the H11B1 (the 2nd diagram on the page)... I'm probably not reading something right. http://www.mikroelektronika.co.yu/english/product/books/PICbook/7_05chapter.htm
  • MazdaMazda Posts: 5
    edited 2006-04-03 18:46
    Is there an IC you'd recommend with multiple transistors for driving all the relays?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-04-03 20:18
    Okay,·apparently that opto can handle the relay specified, although it says that's a 7.5V relay.· In automotive applications you would typically be running a 12V Relay at voltages up to 15V.· In any event, I'm not so sure that circuit is correct anyway as it shows a Darlington opto, but the Collectors are not tied together, which they should be.· It really boils down to the ratings of the device (in this case the relay) you're trying to drive.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Vern GranerVern Graner Posts: 337
    edited 2006-04-03 20:42
    Mazda said...
    Is there an IC you'd recommend with multiple transistors for driving all the relays?

    The venerable ULN2803a, sold right here by Parallax. [noparse]:)[/noparse] Commonly used in relay board kits and even as a standard part in the Prop-1 controller. For $1.50, you can control 8 relays and you don't have to put in back emf diodes as they are built into the chip. The part can handle up to 500ma, so it's beefy. I've used this chip to operate small motors/ relays and have had zero failures. I've only killed one of these and it was through operator error (fed the part inverted 48vdc!)

    smile.gif

    Vern

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Vern Graner CNE/CNA/SSE    | "If the network is down, then you're
Senior Systems Engineer    | obviously incompetent so why are we
Texas Information Services | paying you? Of course,if the network
http://www.txis.com        | is up, then we obviously don't need
Austin Office 512 328-8947 | you, so why are we paying you?" ©VLG

    Post Edited (Vern) : 4/3/2006 8:48:08 PM GMT
  • MazdaMazda Posts: 5
    edited 2006-04-03 21:48
    Excellent.· Just what I was looking for.· Are there similar chips to combine multiple optoisolators (4N25)?
    Vern said...
    Mazda said...
    Is there an IC you'd recommend with multiple transistors for driving all the relays?

    The venerable ULN2803a, sold right here by Parallax. [noparse]:)[/noparse] Commonly used in relay board kits and even as a standard part in the Prop-1 controller. For $1.50, you can control 8 relays and you don't have to put in back emf diodes as they are built into the chip. The part can handle up to 500ma, so it's beefy. I've used this chip to operate small motors/ relays and have had zero failures. I've only killed one of these and it was through operator error (fed the part inverted 48vdc!)

    smile.gif

    Vern

  • Vern GranerVern Graner Posts: 337
    edited 2006-04-03 22:58
    Mazda said...
    Excellent. Just what I was looking for. Are there similar chips to combine multiple optoisolators (4N25)?

    Well, there's the NTE3221 Quad Opto isolator carried by Jameco (Jameco P/N 273607). Would that suit?

    smile.gif

    Vern

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Vern Graner CNE/CNA/SSE    | "If the network is down, then you're
Senior Systems Engineer    | obviously incompetent so why are we
Texas Information Services | paying you? Of course,if the network
http://www.txis.com        | is up, then we obviously don't need
Austin Office 512 328-8947 | you, so why are we paying you?" ©VLG
  • MazdaMazda Posts: 5
    edited 2006-04-04 00:18
    Man, I should've checked this thread before ordering... I ordered PS2501-4A-ND from Digikey.· Hopefully that will work.

    RFID and LCD are from the Parallax store [noparse]:)[/noparse]
    Vern said...
    Mazda said...
    Excellent. Just what I was looking for. Are there similar chips to combine multiple optoisolators (4N25)?

    Well, there's the NTE3221 Quad Opto isolator carried by Jameco (Jameco P/N 273607). Would that suit?

    smile.gif

    Vern

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