Assume I know nothing and need lots of help !

[sparks_vfr]

Hi guys, have been mooching round the board for a little while and thought I'd register and ask a few questions as I have been asked to help a friend and thought with your help I'd be able to help him (if that makes sense)


The plan is to monitor an array of various pressure and temperature sender units fitted to an engine test rig (Radial Aero engine).. The data is then sent via a serial (usb) interface, then a little software (Am part time programmer so no probs there) and the data can be saved realtime to a file for examination at a later date, and/or displayed..

In my simple way of looking at it, all I need to do

1. Check resistance on each of the sensors (Using standard car sensors)
2. Send the data via an interface through usb/serial port
3. Read in data and display/save

I do have some minute amounts of finger melting skills and have done some basic projects, but if some kind soul could give me some pointers I'd really appreciate it


Many Thanks

Sparks

 

[Norlin]

sounds like you want to grab a hold of a microcontroller programmer, a microcontroller with some ADCs to read your resistances and EEPROM to store the data in. Reading it out via serial is probably your easiest bet as USB tends to get more tricky.

 

[sparks_vfr]

Thanks for that, I guessed would need an ADC, just not sure about microcontroller info etc..

Microcontroller to perform what action, convert the value into an easy to read value ? (Sorry if am being particularly dim)

I have found this https://www.xdesignlabs.com/xlogger.php which at first glance appears to do what I need at a very good price, probably less then i could make one for, but would still like to have a go at building one

Sparks

 

[sparks_vfr]

Have dug around some more and found this little baby that seems to fit my needs... However, how would I get to monitor more than 1 sensor (I need approximately 16!)?

https://www.iguanalabs.com/adc2051.htm

I have also found this https://www.xdesignlabs.com/xlogger.php which seems to fit the bill pretty much, I probably wouldn't be able to build one cheaper, but would like to try anyway


Sparks

 

[Cry_Wolf]

Why not save the data in the PC? On the hardware side just digitize the data and transmit to the PC via serial port and the application on the PC will acquire the data and save it.. I think no need of EEPROM

 

[sparks_vfr]

That is my plan to save it to the PC..

And why are my posts not showing !!!

Sparks

 

[Norlin]

Ah, some reason I thought he'd be gathering the data while the engine was in use, then retrieve the data at a later point to his PC, but if the PC can be connected while the data is being logged, there's no need for the EEPROM

 

[Norlin]

In fact, if he has a live connection, there's no need for a microcontroller even, just some ADC ICs and connect that up to the PC via a MAX232 or something and write a program.

 

[sparks_vfr]

Odd !! thats my third reply ..

I had links in my other posts will that slow things down ?

Ok quick re-cap, on posts not shown lol..

Found a datalogger with ADC for 139USD (xlogger by xtal), 10 channels, I doubt I could build one for less but would like to have a go anyway.

What would I need the microcontroller for ? Would it be to make sense of the info from the sensors ?

By just throwing the raw data at the serial port what would I expect to see ?

Could I interpret the data with a bit of code ? (Which should be easy enough as long as I know what the raw data will be)

The way I understand the sensors is that they are basically a resistor which reduces or increases in resistance depending on the pressure/temperature..

Sparks

 

[Cry_Wolf]

In fact, if he has a live connection, there's no need for a microcontroller even, just some ADC ICs and connect that up to the PC via a MAX232 or something and write a program.

How will he make the data serial?
He mentioned that there are more than one sensors! so he need to multiplex
So i think that a controller is a must!

 

[sparks_vfr]

Sorry, maybe I should explain things a bit...

It's for monitoring an aircraft engine (7cyl radial) on an engine test stand.. A laptop running Linux (As if there were any other OS's worth discussing )

Plan is to read the sensor data in through the serial interface and log it directly to file for analysis later, also to have a real-time display for monitoring purposes..

Once this is completed I plan to move the project on to log data on an eeprom, so the unit can be used in-flight.. The aircraft is a YAK15, so is not the most up-to-date technology wide !

Sparks

 

[sparks_vfr]

How does the multiplexer work ? Does it take a reading from each sensor, and pass it on in order ?

Sparks

 

[Cry_Wolf]

if you use a microcontroller then i suggest you use a ADC 0808 (Analog to Digital Converter). It can take 8 analog inputs and multilex them as well Giving the digital out put of one Analog input at a time. Perfect for your case!

 

[sparks_vfr]

Ok, so have had a read of the info on the ADC0808, it does look pretty much perfect apart form being half the size I need..

Could I use 3 ..

first one collecting data from 8 sensors second collecting data from another 8, the thirst collecting data from ADC 1 and 2, then sending that to the PC ?

the timing circuit am assuming is just a 555 ?

Sparks

 

[Cry_Wolf]

You are totally wrong. First tell me how many Analog signals you need to monitor? are they 16?

 

[sparks_vfr]

yes 16

Sparks

 

[Norlin]

What I was thinking was a multi-channel ADC that has a serial output (rather than parallel), hook it to a max232 then to the PC, on the PC you wouldn't use a terminal, rather you'd write a program (as you would for a microcontroller) to speak to the ADC across the serial port...wouldn't that work? Basically replacing the uC with the PC.

 

[Nigel Goodwin]

What I was thinking was a multi-channel ADC that has a serial output (rather than parallel), hook it to a max232 then to the PC, on the PC you wouldn't use a terminal, rather you'd write a program (as you would for a microcontroller) to speak to the ADC across the serial port...wouldn't that work? Basically replacing the uC with the PC.

It's not as simple as that, a serial ADC can't just connect via RS232, it's a syncronous output, NOT an asyncronous one - easiest way is a micro-controller with in-built A2D, and connect via RS232.

 

[Cry_Wolf]

ok then you will be using two ADC0808 (I dont know if an ADC for 16 analog inputs exists or not?) The third IC will be a microcontroller. The 1st ADC's output goes to the first port of the microcontroller and similarly the 2nd ADC's output to the 2nd port. Next the microcontroller will be controlling the select lines of the two ADCs. There are three select line for each ADC.
If you use 8051 controller probably you can get a ready to use interface for the serial port.

Ok now coming to the programming algo of the microcontroller

START:
1- Send 000 to the select lines of 1st adc and read the analog value on the portA and send it to the serial interface.

2- Send 001 to the select lines of 1st adc and read the analog value on the portA and send it to the serial interface.

3- Send 010 to the select lines of 1st adc and read the analog value on the portA and send it to the serial interface.

4-Send 011 to the.......

5-Send 100 to the.......


6-Send 101 to the.......


7-Send 110 to the.......


8-Send 111 to the.......


9- Send 000 to the select lines of 2nd adc and read the analog value on the portB and send it to the serial interface.

10- Send 001 to the select lines of 2nd adc and read the analog value on the portB and send it to the serial interface.

11- Send 010 to the select lines of 2nd adc and read the analog value on the portB and send it to the serial interface.

12-Send 011 to the.......


13Send 100 to the.......


14-Send 101 to the.......


15-Send 110 to the.......


16-Send 111 to the.......

GO TO START

 

[Cry_Wolf]

easiest way is a micro-controller with in-built A2D, and connect via RS232.

I agree ..