Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

protection of PIC18f452

Status
Not open for further replies.
S

shaneelal

Member level 1
Joined
Nov 16, 2004
Messages
38
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
553
I need help with something.I"m using a sensor which can output -6Vdc to 6Vdc. I'm using a potential divider to get max of +5V entering my PIC18f452. I would like to be able to safe guard my PIC for negative voltages and voltages greater than +5V. What should I do to protect the PIC?
 

Hi,

You're trying to read a -6 to 6V signal by the AD input of PIC18, rigth?

To read this you need to change the sensor signal form -6 to 6V to 0 to 5V, to do it use Operationals Amplifier, attached is a block diagram for it. To protect the PIC you can put a OP with Gain = 1, suplyed by the 5V circuit, like us showed in the picture attached.

If I help you, please click in the Helped button.

Emanuel Cassimiro da Silva
 

    S

    shaneelal

    Points: 2
    Helpful Answer Positive Rating
If the case is a positive/negative symmetric wave (maybe a sine wave) and you can look only at the positive cycle, a way is in picture.
With this the errors added to you wave supplied to the ADC are minimized....
NOTE: You must calculate the voltage divisor related to the ADC reference, and resistors should have 1% tolerance.


HH
NeuralC
 

    S

    shaneelal

    Points: 2
    Helpful Answer Positive Rating
Thank you for all your help.I've attached the spec sheet for the sensor. The sensor can measure +/-600Amps. The output is +/-6V. If I'm measuring only 0-600Amps, should I cater for the -600Amps? Would the 0-600Amps output only 0-6V?
I would then use a potential divider onto PIC,so maximum it can recievce is 5V.
The spec sheet isn't too user friendly,so I wrote the manufacturer and asked him some questions,the answers are on the side of the questions.

Code: 
1. Is the input range +/-600 or 0 - 600Amps? +/-600 ADC or Peak AC

2. Is the output +/-6V or 0 - 6V? +/-6VDC or Peak AC

3. Is the power supply +/-15Vdc or 0 - 15Vdc? +/-15Vdc

 

 

Regards,

 

Jim McHan

Senior Applications Engineer

Export Compliance Officer

Sypris Test & Measurement, Inc.

6120 Hanging Moss Rd.

Orlando, Fl. 32807
 

It looks a 6V peak, so if you are measuring sine power line, you can only care about the positive peak. You algorithm should calculate the RMS (I suspect) value…
A note is, be careful with the reference of ADC, normally +5v power supply have high float level, so, power the sensor with same source(but source needs 15v) or use a high resolution reference (maybe using LE45)

HH

NeuralC
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top