Note to all - this is not my thread. My credit on the header is purely accidental. I even managed to lose the OP's name.
<OP>
Well Newbie here. Let me state my application,and that I have read the data sheet. Also I have a limited experience with IC chip replacement. I am using a LM2917N-8 chip to repair an electronic Speedometer from a Kawasaki motorcycle. I have the chip in place on the original circuit board in a IC socket. I have 4 chips, I case I blow one experimenting. I have rerouted my printed circuit to match the circuit needed. 470 ohm resistor on input voltage as well as another zener, C-1 = .01uf, C-2 = 1.0uf, R-1 = 100K, and at R-2 I have a 500 ohm pot to ground at pins 4-7 for trimming. The Full scale voltage needs to be about 3.7v, meter coil resistance is 80 ohm.
My problem is the input signal, it comes from a 3 wire sensor on the front wheel. 1-ground, 1-B+, 1-signal return. This has a switching voltage between .5-6.5volts, frequency is variable with wheel speed. I believe what I need to do is put the input signal through a "AC Coupling" as I know my signal is not going below ground.
Can someone help me with how to complete this circuit for the AC Coupling? I found the circuit on the Data sheet but it does not explain the values for the resistors or the connection of the transistor, PNP or NPN? I've never built one before, and it sounds like it would be fairly simple.
OK I found some info in the forum for this, I have a single pole DC square wave that needs to be changed to a BI-polar square wave. There is a capacitor and some resistors that need to be added to this in-put to LM2917. So still have not found a "clear explanation" of this addition. Please point me to another thread or jump in this one with some help. Thanks.
So do I take the output from my 3 wire sensor and put it to the input of my LM2917 with a 1uf cap in series or parallel? I read on the Data sheet about inputs through a 10Ω resistor? Is this also needed?
I have a new post about my speedometer repair using the LM2917N-8 chip.
It has my schematic/ values. Thanks for such a great forum.
<end OP>
<moderator>
That was a 5 year old thread you hijacked - http://forum.allaboutcircuits.com/showthread.php?t=276
That is one reason why we ask that people start new threads for new questions. It saves confusion.
I would try the cap in series with the signal. If the signal is too great in magnitude, you may have to use a resistive divider to reduce it. Can you measure the pulse train with a meter?
<end moderator>
<Sgt.Wookie>
Could this thread be merged in as a reply to Motor head's 1st thread, here?:
http://forum.allaboutcircuits.com/showthread.php?t=25880
That would help give some continuity as to his project.
<end Sgt.Wookie>
<OP>
I will wait for the replay on my new thread, Thanks.
<end OP>
Apologies to all for such a cruddy merge - moderator did poorly.
<OP>
Well Newbie here. Let me state my application,and that I have read the data sheet. Also I have a limited experience with IC chip replacement. I am using a LM2917N-8 chip to repair an electronic Speedometer from a Kawasaki motorcycle. I have the chip in place on the original circuit board in a IC socket. I have 4 chips, I case I blow one experimenting. I have rerouted my printed circuit to match the circuit needed. 470 ohm resistor on input voltage as well as another zener, C-1 = .01uf, C-2 = 1.0uf, R-1 = 100K, and at R-2 I have a 500 ohm pot to ground at pins 4-7 for trimming. The Full scale voltage needs to be about 3.7v, meter coil resistance is 80 ohm.
My problem is the input signal, it comes from a 3 wire sensor on the front wheel. 1-ground, 1-B+, 1-signal return. This has a switching voltage between .5-6.5volts, frequency is variable with wheel speed. I believe what I need to do is put the input signal through a "AC Coupling" as I know my signal is not going below ground.
Can someone help me with how to complete this circuit for the AC Coupling? I found the circuit on the Data sheet but it does not explain the values for the resistors or the connection of the transistor, PNP or NPN? I've never built one before, and it sounds like it would be fairly simple.
OK I found some info in the forum for this, I have a single pole DC square wave that needs to be changed to a BI-polar square wave. There is a capacitor and some resistors that need to be added to this in-put to LM2917. So still have not found a "clear explanation" of this addition. Please point me to another thread or jump in this one with some help. Thanks.
So do I take the output from my 3 wire sensor and put it to the input of my LM2917 with a 1uf cap in series or parallel? I read on the Data sheet about inputs through a 10Ω resistor? Is this also needed?
I have a new post about my speedometer repair using the LM2917N-8 chip.
It has my schematic/ values. Thanks for such a great forum.
<end OP>
<moderator>
That was a 5 year old thread you hijacked - http://forum.allaboutcircuits.com/showthread.php?t=276
That is one reason why we ask that people start new threads for new questions. It saves confusion.
I would try the cap in series with the signal. If the signal is too great in magnitude, you may have to use a resistive divider to reduce it. Can you measure the pulse train with a meter?
<end moderator>
<Sgt.Wookie>
Could this thread be merged in as a reply to Motor head's 1st thread, here?:
http://forum.allaboutcircuits.com/showthread.php?t=25880
That would help give some continuity as to his project.
<end Sgt.Wookie>
<OP>
I will wait for the replay on my new thread, Thanks.
<end OP>
Apologies to all for such a cruddy merge - moderator did poorly.
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