Assuming 450 pulses per litre = 7.5Hz per litre per minute gives an alarm frequency of 90Hz, and a maximum frequency of about 300Hz.That sound quite good. I wonder if you could come up with schematic for the 2 x 555 option.
If it makes it any easier for you , you could put it on paper, scan and attach here. Then I'll turn it into a project using Easyeda and publish the schematic & board in this forum for any corrections if needed.
Will not work with only a 5 volt TTL output from the sensor. Have you tried this circuit?It’s pretty much a classic watchdog timer circuit.
Features:I'm assuming that the output is open collector
I agree. I certainly do not see a 5 volt regulator chip on board. The output specs are misleading.I'm still assuming that the output is open-collector
Why the bridge? Is the supply voltage 12 volts?made a (new)rectifier bridge with schottky diodes 1n5819
Yeah those are some of the same specs I posted earlier but I don't believe those are accurate. If you are using a 12 volt supply then you should see 12 volts out when the magnet is not near the hall effect sensor.I found the following maybe it's of any use:
by Jake Hertz
by Jake Hertz
by Duane Benson