Hall Sensor switch and alternating transistor?

[albersondh]

I need a couple parts for a project I’m working on but with my limited knowledge I’m not even sure what to call them. I will try and explain:

- I need to take a signal from a hall sensor (crank/RPM sensor 5vdc) and use this signal to close a switch (relay/transistor) at a adjustable Hall output frequency. Sort of like an adjustable shift light, but with the signal coming from the Hall sensor. Any ideas on what I can use to make this happen?


- This one is simple. I just need a relay/transistor that switches between two independent circuits every time a signal (base) voltage is applied. A signal voltage should trigger the switch closed, but it needs to alternate between closing two independent higher current circuits. Every time signal voltage is received I need it to switch from closing one higher current circuit to another. What can I use?

This is all automotive application so the circuits other than the hall input will be passing 12vdc. I really, really, appreciate any help.

 

[duffy]

For the second one, have a look at this thing -
Digi-Key - PB513-ND (Tyco Electronics <!--Potter & Brumfield--> - S89R11DAC1-12)

It's a 12V relay that alternates loads with each activation.

For the first one, it sounds like you need a frequency-to-voltage converter and a comparator. You want the thing to come on at or above a certain frequency, and be "off" below it, right?

 

[albersondh]

For the first one, it sounds like you need a frequency-to-voltage converter and a comparator. You want the thing to come on at or above a certain frequency, and be "off" below it, right?

Exactly ^. I need to determine what freq/RPM I need to actuated the switch at. So it would be great if it has a pot that will allow me to adjust the point that it actuates the switch. This will be a test item, once I nail down what freq out-put = what RPM, I can lose the pot and just trigger the switch at a specific freq. Thanks for the help.

 

[ccurtis]

This a pretty simple circuit, made simple by the complexity of the device used in it. It uses Duffy's relay and makes no assumptions about what you are powering the Hall device with, as long as you get the full 0 to +5v swing out out the Hall device. It will energize the relay when the speed threshold is reached and will not de-energize the relay until the speed drops below the threshold.

 

[albersondh]

This a pretty simple circuit, made simple by the complexity of the device used in it. It uses Duffy's relay and makes no assumptions about what you are powering the Hall device with, as long as you get the full 0 to +5v swing out out the Hall device. It will energize the relay when the speed threshold is reached and will not de-energize the relay until the speed drops below the threshold.

How is the speed/freq threshold determined, I didn’t see a pot? When some value is greater than another?? Also what’s that thing at TIP30, looks like a transistor?? Forgive the ignorance.

 

[ccurtis]

How is the speed/freq threshold determined, I didn’t see a pot? When some value is greater than another?? Also what’s that thing at TIP30, looks like a transistor?? Forgive the ignorance.

You have to translate your desired speed threshold into frequency (pulses per second at the output of the Hall device). Resistor, R, in the schematic is your pot. The threshold frequency is given by the equation at the top of the schematic; 1÷(2×R×C), where Resistor, R, in ohms; Capacitor, C, in farads. The data sheet for the device gives limits which bound the value for R and C, but the device works for frequencies from 0 to 10,000 pulses per second.

The symbol for the transistor did not come out readable, sorry. The emitter is at the top, collector at the bottom, base on the left.