What's wrong with my LM-2907

[mustang98]

I've set my circuit up exactly as shown in the data sheet that describes the LM2907/2914 and my voltage out changes very slightly on a big change of RPM. For example: a change of 1,000 rpm only gives me a difference of .14 volts. Any ideas on why my span is so short?

Thanks

 

[indecided]

I've set my circuit up exactly as shown in the data sheet that describes the LM2907/2914 and my voltage out changes very slightly on a big change of RPM. For example: a change of 1,000 rpm only gives me a difference of .14 volts. Any ideas on why my span is so short?

Thanks

Mustang, please post the specific schematic you used. Also, how many cylinders does your car run, and where did you tap your TACH output from?

I had this problem a while back where there would be hardly any voltage change. I'm guessing you're running this through a comparator to switch on an external load? What exactly do you want the source voltage to run, a LM3914? bargraph driver?

 

[chemelec]

Which Circuit? There are Quite a Few.

For a Car Motor?

Using a Reluctance Pickup?

Are you Sure you have an Appropriate Signal?