View Full Version : telemetry for DC voltage(100volts) and Current(20amps) over 100 meters

lee cabe
01-14-2007, 01:05 AM
We have a high school solar car in Newburgh NY and wish to bluetooth link V and I readings from our solar car to a bluetooth dongle in our chase vehicle laptop.· We are neophytes in this endeavor and need to know what components we need to·sample·V and I every minute and then graph them.· We understand that we can send via an embedded blue tooth transceiver.· We hope·we can utilize our·basic stamp 2 to send this info but need to know the easiest way to digitize our V and I, what sensors would be best and how to set up the bs2.· We also would appreciate· and info on sending via bluetooth and reading that info on a real time graph.

Thanks for any info
Lee Cabe
Sol Machine VI

01-14-2007, 01:57 AM
Use AD converter to sample the voltage and current using dividers to reduce the values to those managable by the sensors and then send those readings to the chase vehicle. Let the computer in the chase vehicle do the math.

- Stephen

lee cabe
01-14-2007, 02:17 AM
Understand use of AD converter, guess we obtain these fromparallax components. Do not follow dividers, we were using resistors in parallel to reduce voltages to 5 volts. By letting the computer do the math I guess you mean excel.

01-14-2007, 02:39 AM
I have used Allegro Micro's ACS754 current sensor in a project where I had to monitor current draw of a hydrogen cell (~50amp peak). The sensor is a good choice over standard shunt resistor methods because it doesn't cause voltage drops since it's internal resistance is extremely low. It is possible to request samples from Allegro as a high school student (thats what I did).


Note that you will need to have an ADC to interface with this sensor since it outputs a linear voltage that corresponds to the current through the sensor.

For voltage, you should be able to use a resistor voltage divider (aka resistors in series) to reduce the voltage down to a 5v max signal voltage required for standard 5v ADCs. Note that you may want to put a 5.1v zener diode on the output of the divider to clamp the voltage at a max of 5.1v so you don't fry the ADC in the event of over voltage.


Post Edited (Harrison.) : 1/13/2007 7:45:33 PM GMT

lee cabe
01-14-2007, 03:09 AM
gotcha Harrison
We will goto allegromicro.com and will use the 5.1v zener diode for protection. This is the info we are thirsting for. We are brand new to the BS2 are about to try some experiments to see how it works how we can communicatewith it.

Kevin Wood
01-14-2007, 03:49 AM
Here is a page for you to check out for realtime graphing software & wireless telemetry modules: www.selmaware.com (http://www.selmaware.com)

Martin Hebel, the man behind SelmaWare, is active on these forums. He can answer any questions about the products, if you have any.

lee cabe
01-14-2007, 03:59 AM
Thank you Kevin
The software problem is one of our nightmares and selmaware.com looks like an answer to a prayer. We will check into their website.

Kevin Wood
01-14-2007, 05:33 AM
If you want to see some info on StampPlot Pro in action, download the Industrial Control & Process Control books from the Parallax site. The software is used for these courses.

Here's a link: www.parallax.com/html_pages/edu/curriculum/sic_curriculum.asp (http://www.parallax.com/html_pages/edu/curriculum/sic_curriculum.asp)

Martin Hebel
01-14-2007, 05:54 AM
Just wanted to say hi since Kevin says I'm listening :) If I can be of help, yell.
- StampPlot & Wireless stuff...


Martin Hebel
StampPlot - Graphical Data Acquisition and Control (http://www.stampplot.com/)
AppBee -·2.4GHz Wireless Adapters & transceivers·for the BASIC Stamp & Other controllers (http://www.selmaware.com/appbee)·