Telemetry system ideas

edited October 2012 in IET Formula 24+
Hi all,

Coming in to the new racing season our team (Pit Lizards) is looking at implementing an automatic wireless transmission system for our car's engine temperature, battery current & volts and the speed it is travelling at. These measurements would be transmitted periodically, say every 30 seconds of racing time, to the pit crew who could then use the data to advise the driver.

Do any other teams have this kind of system, and how do you do it?

Currently we are looking at using a Raspberry Pi as the computer to transmit the data along with a digital voltmeter, ammeter, thermometer and speed measuring device. So far we have found that USB ports would be the most suitable to connect the whole thing together, but we're not sure about wiring it all up or programming the devices correctly to transmit.

Any advice would be appreciated, cheers.

Comments

  • I believe a Pi would fall foul of the no additional batteries for data logging etc rule.
  • edited October 2012
    Yes, quite a few teams have and are using telemetry systems. I think it is an excellent way to see what the car is doing, provide data for the STEM aspects of GP and investigate the science and control algorithms. It also allows the engineering orientated students to actively engage in a race even when not driving. The data can be used in many ways as well as optimising the performance of the car. It also offers the ability to show the pupils a major aspect of Green devices and electronics control of them.
    As with anything in engineering, there are many ways to do this all with pros and cons. Some things I would suggest:
    1. As in general with GP, keep it as simple as you can at first. Once you have something working it can be
    extended.
    2. Try and make sure there is someone who can understand how it works and show/involve the students in the
    work. (Local Electronics engineers (IET members ?))
    3. The major item to decide on is what to use for a radio link. The main ones are 434MHz, 869.85MHz and
    2.4GHz Zigbee all bi-directional and all are available as small modules. The XBee modules are quite
    popular. It is also possible to use a GPRS mobile data link, but that would cost in phone bills and power usage.
    4. Generally you will only get reception line of sight. On some circuits that will just be the track by the
    pit lane. So it is useful to store the data on an SDCARD for later analysis.
    5. Calculating average for things is useful as you only see the data rarely and things like voltage and current
    vary all over the place on a lap.
    6. The Raspberry Pi is not really suited to this application. It is more of a standalone general PC like
    computer board and has no IO (input/output) abilities to speak of. Something else would have to
    sample/measure the values of things and the Raspberry Pi would just be sending it. Not a lot of work for
    a Linux based computer! However, it can be used and if you intend to use a GPRS mobile link it might be
    useful for ease of development.
    7. A PIC/Picaxe, Ardino or smaller ARM system would probably be best though. These often have lots of IO
    ability to read temperatures, speed, current etc. (I am considering making as small ARM module available
    that could be used on a simple kit or DIY board for this).
    8. As Josh says, the power would probably have to come form the main batteries, depends if GP's
    technical committee modify the rules from team feedback. A simple regulator with spike protection
    would handle this if batteries are not permitted. (All of our electronics is powered from the main batteries)
    9. You will want a battery backed up real-time clock to time-stamp the data. (I hope these coil cell batteries will
    be permitted ...)
    10. Although the RF modules will likely be bi-directional, you may not be able to use the sending to car function for driver information/control etc due to the new rules. (I really do hope this rule is changed ...)

    Information on the system we designed, built and use is at: http://www.greenpower.beamweb.co.uk/files/CarComputer/index.html
    This is based on simple PIC processor (PicAxe or PIC). This was done as the pupils use these in DT lessons. The boards were built by the pupils. This has served us well over the years and has been changed and extended as time and needs change. It also drives the motor via a pupil built speed controller.
    The data logs from all our races (Have to put the latest ones on) are at:
    http://www.greenpower.beamweb.co.uk/files/RotaryRacer/performance/
    Should give you an idea of the sort of readings to expect. We sample the data every second

  • Thanks to Terry for taking the time to share his excellent experiences - a theme which is ever increasing within Greenpower.

    Measuring things gives you confidence that you are in control and provides more inspirational thoughts that lead to better products and better engineers that can design and build better products. As long as this country relies more and more on imports from abroad, we will become poorer and poorer as a nation.

    I am very much in favour of inspirational information and not in favour of rules that stifle its creation.
  • Yes I would add my thanks to Terry for the generous way he and his team have shared information. We are also developing a telemetry system and hoping to increase the pupil involvement in the programming and design, which can only be a good thing.

    We are still of the opinion that small batteries (pp9 and smaller) would not be a bad thing and would make fewer dangling wires and interfering transients without in any way adding to the traction battery capacity.
  • Couldn't agree more! I can't see any problem with small auxiliary batteries. I would be happy if the rules state something like, "The power to the drive motor must only come from the main batteries that Greenpower specify for that purpose. No other significant energy source must be supplied to the main batteries." That way we still allow other kit to be powered, and/or the use of self-powered devices. The electrical safety rules will still apply regardless of any power source.

    On the subject of dangling wires....two years ago one car came in to the pits with glowing wires across the drivers overalls - and the power was "off".....Keeping it separate reduces the risk of injury.
  • edited October 2012
    Thanks, I just hope the info is of some use and helps, rather than hinders :), encouraging more people into engineering.
    I've put an electronics area on our website, if any one wants to contribute some electronic GP ideas let me know and I will provide a login.
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