Pulse doubler schematic

[Bruce Plecan]

-----Original Message-----
From: Steve Ravet <steve.ravet at arm.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Thursday, October 01, 1998 6:38 PM
Subject: Re: Pulse doubler schematic


>jdzura at csc.com wrote:
>>
>> >I think I like Bruce's original idea the best, though.  Two 555s, each
>> >in monostable mode, one on the positive edge and one on the negative.
>> >That's one IC (556) plus some passive components, plus a couple
>> >transistors to combine the outputs.  Battery voltage works fine.  It
>> >also avoids programming the PIC.  You won't get a 50% duty cycle at all
>> >speeds, but it doesn't sound like that's a problem since the ECM uses a
>> >zero crossing detector.
>>
>> I agree, KISS (keep it simple s.....) where ever possible. The only thing
I worry
>>       about is the drift and resulting pulse width change over time and
>>       temperature.
>
If it has an electric speedo then there is no need for the conversion.
This whole thread started on the 730/165 interfaces.

Doing the software changes from the posting the other night we can
run the 730 off of a 12v DC pulsed VSS.  Now I'm trying to come up
with a hardware answer.

The 165 should be an easier answer.
Cheers
Bruce

>The 555 solution may not be good for driving an electronic speedometer,
>but even with drift it should be fine for the ECM.  As someone else
>pointed out, the ECM doesn't know about the rear end ratio, what gear
>the trans is in (except 4th gear switch on 700r4s), etc.
>
>>
>> If the ECM uses a zero crossing detector, does that mean all the signals
are AC.
>>       Also, what is the Peak to Peak Voltage level? Do we have any idea
of what
>>       minimum pulse width the ECM can detect?
>
>--
>Steve Ravet
>steve.ravet at arm.com
>Advanced Risc Machines, Inc.
>www.arm.com
>