Shop OBEX P1 Docs P2 Docs Learn Events
Driving a tachometer — Parallax Forums

Driving a tachometer

jknightandkarrjknightandkarr Posts: 234
edited 2010-02-14 13:28 in Propeller 1
I just wondered it there was anyway I could drive a GM tachometer to test it with either the Propeller or the BS2? I need to test one, & don't have access to a running GM vehical.

Joe

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
I'm going insaine. It's SOOOOOO much fun. lol

Comments

  • HughHugh Posts: 362
    edited 2010-02-03 10:27
    If its one that just counts pulses then it could be quite straightforward.

    If its one that receives data on the CAN bus it could be a lot less straightforward....

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Hugh - the thinking woman's Geoffrey Pyke.
  • jknightandkarrjknightandkarr Posts: 234
    edited 2010-02-04 18:37
    I tried it once with the BS2, while it will drive an my electronic speedometer, i couldn't get it to drive the tach.

    Joe

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I'm going insaine. It's SOOOOOO much fun. lol
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2010-02-04 23:06
    I'd try 12V pullup resistor to a npn transistor.
  • yarisboyyarisboy Posts: 245
    edited 2010-02-14 13:28
    I solved the problem by running a Prop output through a LM324 with gain resistors that boost the signal up to 0-to-12 volts square wave just like comes out of the pin on your OBD2 connector. For simplicity I used the Propeller Spin Studio board with a prototyping square plugged into it. The scope trace from this arrangement is identical to that generated by my Toyota ECU feed to the OBD-II connector. Toyota (in '08) also uses the twisted pair buss between its 8 micro-controllers all over the vehicle. I swapped one of the two gain resistors required with a 10-turn board-pot so I could get exactly 12 volts output. I fed my Op-Amp power from an old printer power supply because the Spin Studio board doesn't send 12 VDC up to the proto-typing mini-board. With the external power supply I can boost the signal to 24 volts should an application require it (relay driver ?). This particular Op-Amp can source 160 ma per channel and be feed up to 30 volts. I can expand the board shown to supply up to four channels for a project I'm working on. Sorry about the dust Brian, its Arizona.


    tachsim.jpg

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    MOORE'S LAW: The capabilities of electronics shall double every 18 months.
    cloyd's corollary: Hardware is easy, software is hard.

    Post Edited (yarisboy) : 2/14/2010 2:03:14 PM GMT
Sign In or Register to comment.