Hello all! As mentioned in the title, I am a complete novice in electronics. I am working on a motor, and would like to add a component to the existing circuitry. Probably best explained by the attached pic. Please take a look and let me know if you can point me in the right direction. If nothing else, you'll get a chuckle at my attempt to draw the circuit.

Thanks in advance...
Edit: Just noticed title error, need to add: Novice needs advice on spelling "suggestions"

 

Haven't understood what you are trying to achieve.

 

Are you trying to make a horn alarm sound upon the passing of a temperature or pressure threshold?

 

Sorry for the lack of clarity in the original post. The thermistor part of the circuit is already on the motor, and yes, when the temperature threshold is met, the thermistor closes to ground. When this happens, the warning horn sounds in a continuous tone.
I am looking for a way to add a pressure switch (dotted line in pic), that would also close to ground once the pressure threshold is met. The only thing is, that I would like to recognize a difference in the sounding of the warning horn. I was thinking of some circuit that, once the pressure threshold is met, it would close to ground, reopen briefly, close to ground... etc. This would result in a intermittent beeping of the horn, instead of a continuous tone, like that of the thermistor. Let me know if additional info is needed.

Thanks

 

Do you have a particular pressure sensor that
you are going to use?

Post the details of the pressure sensor or more
details about the system.

This could be fairly simple.

 

Pencil, thanks for responding. I do not have the pressure switch yet. I'm hoping to get one that will work just as the thermistor does, open circuit until threshold is met, then close to provide ground to horn. This could be done easily, but the horn would sound the same for both thresholds (temperature and pressure). It may not be possible to get the ground to "flip-flop" open and closed to create a beeping tone, without tapping into some nearby voltage. I was hoping to avoid doing that. If I did tap another voltage, I suppose that I could use a 555 ic to open and close the ground, which would result in a beeping horn.

My lack of knowledge in electronics, made me want to ask for ideas before purchasing the switch, or any other components. If you can think of a way to get the ground to open and close (once threshold is met) without tapping other voltages, please let me know.

Thanks

 

Pencil, thanks for responding. I do not have the pressure switch yet. I'm hoping to get one that will work just as the thermistor does, open circuit until threshold is met, then close to provide ground to horn. This could be done easily, but the horn would sound the same for both thresholds (temperature and pressure). It may not be possible to get the ground to "flip-flop" open and closed to create a beeping tone, without tapping into some nearby voltage. I was hoping to avoid doing that. If I did tap another voltage, I suppose that I could use a 555 ic to open and close the ground, which would result in a beeping horn.

My lack of knowledge in electronics, made me want to ask for ideas before purchasing the switch, or any other components. If you can think of a way to get the ground to open and close (once threshold is met) without tapping other voltages, please let me know.

Thanks

I haven't thought it through completely, but maybe something like an automobile turn signal flasher (2 terminal) might be able to be used.

I'm just throwing out an idea. Maybe to spark an idea.

 

If you look here http://www.mallory-sonalert.com/2_0.htm and about 1/2 way down, look for "Multi-Tone Alarms", they have something that may work for you.

 

Pencil & Bill, thanks for the suggestions. I'll close this one out by saying that I ended up making a free running pulse generator using a 555 timer, 1 capacitor and 2 resistors. I will have to pull voltage from another area on the motor for it to work. It gives me a 1/2 second beep once every second, which does help distinguish the pressure alarm from the temperature alarm.

Thanks

 

Pencil & Bill, thanks for the suggestions. I'll close this one out by saying that I ended up making a free running pulse generator using a 555 timer, 1 capacitor and 2 resistors. I will have to pull voltage from another area on the motor for it to work. It gives me a 1/2 second beep once every second, which does help distinguish the pressure alarm from the temperature alarm.

Thanks

If this is for a critical measurement, where there is a safety danger when it fails, could you post the schematic of what you've made to ensure it is done correctly and won't fail at a bad time?

 

Is this a marine engine?