LM1949 drivers

Clint Corbin ccorbin at rt66.com
Fri Mar 7 15:11:04 GMT 1997


At 06:19 PM 3/6/97 -0800, you wrote:
>We are on an SAE team designing an electronic fuel injection system.  We
>have completed the design and have a robust system using a Motorola 68hc11
>MCU to generate the injector pulses.  We are feeding the injector pulses
>into a National Semiconductor LM1949 injector driver.  
>Everything seems to work, ie the injectors click on and off, but on the
>oscilloscope we notice that the injectors are only taking about .9 Amps
>peak and a quarter of that on hold.  We have 2 amp peak, .5 Amp hold
>injectors from Seimans.  
>We then hooked up a 15 volt power supply directly to the injectors to see
>how much current they used with straight uncontrolled power and noticed
>that they still only had .9 Amps across them.  The same results were
>reached with two different injectors.    
>We were wondering if anyone has experience with Seimans injectors in a
>diy efi system and if there is a way to get more current through them, so
>they "peak" faster.  Thank you,
>Sean
>
>ps we're running them dry right now for test purposes, I don't know if
>that makes a difference. 
>
>

Only played with the LM1949s a bit, but my first guess would be to check
your sense resistor.  Sounds like it is too large.  JMTCW!

Clint Corbin
ccorbin at rt66.com
ccorbin at intel9.intel.com



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