Date:         Sat, 2 Jun 2012 15:37:50 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Any way to trick the Digijet ECU into generating injection
              pulses without the RPM/ignition signal, for test bench purposes?
Comments: To: tinker man <tinkerman007@GMAIL.COM>
In-Reply-To:  <CAMZgk2M+iOn3A9-TG48UWN97z9jkeXxvc8J==-AB+8bMjQ4qww@mail.g
              mail.com>
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At 05:08 AM 6/2/2012, tinker man wrote:
>I'll get down to testing that myself soon, but was wondering if anyone
>has already tried this or has other ideas.

The output driver is FET equivalent of an open-collector, i.e. it
supplies a ground when it's active and open circuit when it's
inactive.  Connecting and disconnecting things while it's powered is
a no-no.  Damage is cumulative and actual failure may occur some time
later. (General rule on the ECU is not safe unless they specifically
say it is.)

Suggest trying a logic pulser set on TTL and powered from 5 volts.
Check Bentley for specs but I believe it's a 5-volt pulse, so TTL
logic margins may be enough.  Or in CMOS mode, adjusting supply
voltage to get desired output voltage.  Otherwise build a triggerable
555 circuit that will output a pulse stream for you at the desired
voltage.  That may be easiest if you don't have a scope to measure
the output of the pulser.  If the datasheets at National Semi etc
don't have a suitable circuit there will be one somewhere on the web.

Yours,
d