Design of multichannel A/D controlled via RS232

[yiovanni]

Hi,

I am trying to design a circuit to monitor up to eight analog voltages ( 0-5V). So, I need to design an 8-channel A/D with an RS232 interface so I can monitor and control the circuit through a PC ( maybe a Visual Basic program). I am trying to implement the circuit with with the fewest possible components due to space constraints.

I would appreciate any suggestions, ideas, possible existing designs or totaly integrated solutions anything that might put me in the right path !

Thanks,

Yiovanni

 

[devrimaksin]

You can find 8 cahnnel input ADC on the market
check TI for example.
It is also important what is your targetted
sampling rate and resolution

 

[Tornado]

Check with Maxim as well, they have app notes for A/Ds parallel
and serial interfaces.

Tornado

 

[IanP]

A/D PCI cards or any others that you install inside your computer are pretty expecive. If you don't want to spend U$500+ forget about them.

If you don't need 10 thousand samples/sec find a data logger which uses command-response protocol and has RS-232/485 interface.
Usually as command they use short ASCII string and as retururn you receive another ASCII string which contains result of A/D conversion of interrogated channel.
You will be able to configure inputs +/-10V, 0-5V etc.. and in most cases 12bit resolution will be more than enough.
Now, you can write your program in VB, LabView .....and monitor your channels.

 

[yiovanni]

Thanks for the suggestions. I am simply looking for the fewest possible ics so I can put this circuit together. So my question is what is the solution that will allow me to use the smaller number of components. 8 -bit resolution will be fine, and data sampling frequency it is low.

Yiovanni

 

[IanP]

Choose uC with built-in A/D converter. (you can go to www.semiconductors.philips.com ) Eg. P87C552 - 8 -10b A/D 0-5V + UART. Next component you will need is RS-232 driver Eg. MAX202 + 4x100uF caps.

Each input you should protect with 100Ohm resistor (in series) and ZD 5.1V.

And that is it!!!

 

[yiovanni]

Ianp,

Thank you. I'll try what you suggested.

Yiovanni