Is it possible to use the output pin of a pressure sensor and connect it to more than one device. I'm building a model submarine and the depth controller uses a pressure sensor to steer the boat to a given depth.

I'm building a datalogger to work like a kind of black box, recording the prosition of sensors, direction, possibly GPS in the future (if I can get a reading under water). It would be nice to have the detph of the boat too.

This is the logger I'm building.
http://home.arcor.de/d_meissner/d_logg2_engl.htm

EJK

 

There's no real problem doing that. You just need to be aware of what the source impedance of the sensor is, and the input impedances of whatever you connect to it, so you don't overload the sensor (which will then give false readings).

Looking at the datalogger circuit, there's part of it, U1C, labelled 'differential pressure measurement' - is this the input you want?. In order to feed two devices from a sensor like that, it would be easiest to connect both to the output of U1C, rather than directly to the sensor, plus it saves an extra amplifier as well!.

 

The thing is, this pressure sensor is already used in a ready bought depth controller of which I have no schematic. I can find the datasheets of the pressuresensor so pinout is no problem.

I do not want mess with the circuitry of the depth controller (which is in good working order) but if I can connect the output pin of the sensor to the ADC of the PIC I can measure the depth the sub was at a given moment.

The differential pressure sensor is used in a pitot tube (to measure the airspeed of a model) and thus only measures a very tiny pressure difference. IMHO this is why it is tied to an amplifier.

While we are at it. The datalogger has the possibility to dump it data using an RF connection forming a telemetry unit. Since you know a lot about Pics I'll also ask this question here. Could I use one of the rfPIC (rfPIC12F675) for this goal. I can then incorporate the conditions in which data should be stored in eeprom and when it can be transmitted with the pic and use the RF part to transmit the data.

Do you have any expierence with these devices. How do I use these in a circuit, What is the range. I have read through Microchips documentation and not learned very much from it.

Erik Jan

 

If you've got the datasheet of the sensor, you should be able to work it out, just make sure that the extra load of your ADC doesn't load the sensor too much - you may need to add a high impedance buffer.

I've not used one, I've often fancied having a play with one though :lol:

Generally the range of these sort of transmitters is about 200m or so, in free air.