Hello, I have a source (wire from cdi to coil) with 100-250VAC with frequency from 150 - 700Hz depending a rpm on my bike. Im trying to do something like a shift light with one turned LED on some rpms.
I tryed with LM2917 and several options, but it doesn work
The circuit you posted with the LM2907 tach IC does not work because the input (pin 1) of the LM2907 needs a DC path to ground, usually provided by a magnetic pickup.
Try the circuit after adding a 100k resistor from pin 1 to ground.
I can generate a simulation.
What is the desired frequency range and full scale voltage output?
Also, the number of engine cylinders and max RPM?
Also, what is the LED suppose to indicate?
Thank you guys for interesting!! My test bike, have a 1 cyl, and 2 stroke engine. I want to LED lights at the desired speeds (rpm), usually between 6000-8000rpm.
Here is a frequency result from green wire to ground, voltage is from ~150V - 200VAC
2000rpm - 150Hz
3000rpm - 250Hz
4000rpm - 330Hz
5000rpm - 450Hz
6000rpm - 500Hz
7000rpm - 600Hz
8000rpm - 700Hz
9000rpm - 1300Hz
And here is from pickup red wire to ground:
2000rpm - 380Hz
3000rpm - 530Hz
4000rpm - 750Hz
5000rpm - 950Hz
6000rpm - 1000Hz
7000rpm - 1200Hz
8000rpm - 1400Hz
9000rpm - 1530Hz
Voltage on 1800rpm is 0.7VAC, on 5000rpm is 1.5VAC, on 7000rpm is 1.9VAC, on 9200rpm is 2.3VAC.
Please attach your schematics to your posts HERE instead of over at UPLOADS where we cannot open or at PHOTOBUCK that takes a long time to open.
Did you try adding a resistor to ground on the pin 1 input of an 8-pins tach IC so that it has a 0V DC reference voltage? The other input is pin 8 which is connected to ground so its DC reference voltage is 0V.
Please attach your schematics to your posts HERE instead of over at UPLOADS where we cannot open or at PHOTOBUCK that takes a long time to open.
Did you try adding a resistor to ground on the pin 1 input of an 8-pins tach IC so that it has a 0V DC reference voltage? The other input is pin 8 which is connected to ground so its DC reference voltage is 0V.
Please attach your schematics to your posts HERE instead of over at UPLOADS where we cannot open or at PHOTOBUCK that takes a long time to open.
Did you try adding a resistor to ground on the pin 1 input of an 8-pins tach IC so that it has a 0V DC reference voltage? The other input is pin 8 which is connected to ground so its DC reference voltage is 0V.
Today I worked with this schematic (IC is lm2917, 14pin version, a second diode (zener) is 1N4148):
Nothing happen again, 0V on out is always, but between input (ignition coil wire) and ground is 1.6V.
A source is motorbike, diesel car (alternator W signal), and transformer from 230VAC to 2.8VAC, 50Hz.
Since you used an LM2917 IC in an 8-pins case, its 7.5V zener diode was blown up since you connected it to a 12V supply. The heat might have destroyed the IC.
The circuit layout posted in post #10 shows an arrow instead of a 1N4148 diode at its input. It also shows an arrow instead of a diode at pin 11. These diodes might be backwards.
Please post the schematic instead of the circuit layout.
I dont have a schematic from post #10, only this pic The guy made a tachometer with 20 leds on other forum, on Vout he merged to input a LM3914-->Leds.
My problem is 0V on output from lm2917.
I do not know what are the voltage levels of the pulses from your ignition coil.
I do not know which end of the 1N4148 is the cathode since it is not the symbol for a diode. It seems to be backwards.
I do not know if the other diode is a zener diode and I do not know its voltage rating. Again I do not know which end is which.
Then you have destroyed the LM2917 because its datasheet says its maximum allowed input voltage is only +28V.
The diode at the top is connected backwards so it passes the high voltage to damage the input of the IC but it blocks a logic low so the IC will not work even if the voltage is reduced and the IC is replaced.
Then you have destroyed the LM2917 because its datasheet says its maximum allowed input voltage is only +28V.
The diode at the top is connected backwards so it passes the high voltage to damage the input of the IC but it blocks a logic low so the IC will not work even if the voltage is reduced and the IC is replaced.
I have sa speedo sensor (digital speedometer) on my bike with hall effect (without intensity 1=0) 3 wire:
Positive +12VDC,
Negative -ground,
Signal wire.
Should I connect a lm2917 to that sensor? And wich one schematic is good for that sensor?
Thanks!
The signal from your speedo hall effect sensor probably does not go below ground so the 8-pins versions of the LM2907 or LM2917 cannot be used.
One of your schematics has the reference input biased at +0.7V with a diode but the signal input is biased at +8.1V which is odd.
I think the reference input should be biased at half the supply voltage so then the sensor input can swing above and below it easily.
Here's something I threw together.
I'm still not sure what the OP wants for LED indication. Just light up between a certain voltage range?
Output is ~500mv per 1000 RPM
One image at 10000 RPM
One image stepped 1000 thru 10000 RPM
He is making a "shift light" that lights at a certain engine RPM when the gears should be shifted to avoid over-revving the engine.
The datasheet for the LM2907/LM2917 shows a "normal" engine application but the inputs are a magnetic variable reluctance pickup or breaker ignition points for car engines.