telemetry

[Rami]

Hi,

We are in the first year of our competition and we want to send data wireless to be analyzed during the different events and i want to know what is the distance should i consider to design my wireless system???

[rmk36]

Rami,

As you may have read in countless other threads, most of us on the forum offer this advice....

For your first year car, focus on getting a simple car that will run reliably. You don't need cool widgets and gizmos to do well in FSAE. In fact, I'd say no more than 5 percent of teams use telemetry, however I be could a little off.

[Tickers]

Why do you want it? At the event, car to pit telemetry serves little to no purpose. You can't bring the car in or signal the driver easily, so what do you gain?

If you want to preserve the car, give the driver two warning lights; one to tell him to ease off and try to make it to the finish, and one to tell him to stop immediately. At the event, the criteria for the second light should be extremely high, you should never willingly stop in endurance unless there's a safety risk, it's always better to crawl to the end otherwise.

However, if you have pit to car telemetry you can make changes to the car to accommodate problems as they occur, taking the need to ease off away from the driver by limiting power/fuel use etc.

The only other time telemetry has real use in FSAE is during testing. With a telemetry system you can leave the car on track indefinitely, monitoring the health remotely and only bringing it in when issues start to arise.

[Rami]

OK,let me address you with our situation. I am the head of the electronics team and my major of study is communication and electronics so by now we don`t have any problems by applying telemetry in the car as its our field of study other than other teams which don`t have that type of engineers in the team. so i think it is not a problem for us to design and build a telemetry system using the PE ECU which make things easier. we have designed our system taking into consideration that maximum distance between the driver and the team would be no longer than 1 KM but we recently discovered that this distance may be longer than 2 KM so i want the exact distance that we should design on it!!!!
and thanks for your advices guys but really this is my job in the team fro the beginning.

[Michael Royce]

Rami,
The range you will need depends on where you expect to have your receiving station.

If it is to be back in the pits, you will need to figure out how far the pits are from the farthest point used for the dynamic events. The farthest we have had in the UK, USA and Australia was at Virginia which is no longer an event. Other than that, the maximum distance of any part of the dynamic track at California, Michigan or Silverstone (UK) is probably about 1 km.

If you hope to have your receiver at track side, the distance would probably be half that.

[BeunMan]

Standard 2.4 wifi (>250mW txpower) does well with 'standard' bipolar antennas's for most of the tracks. (~500m range in normal weather conditions), to keep it simple. If you use wifi you don't need adaptors.
Keep in mind that the 2.4 GHz band is full of crap at events and other bands (e.g. 900 mhz) are not legal in most countries but you probably know this. *looks at 1 Watt 900 mhz transmitters from the US and thinks about telephone signal of GSM in europe/asia*

Now to the point of 'telemetry'. If you can download all the collected DAQ data < 2 minutes after a Endurance test you are fine with wires. Most teams either do this by RS232 or equivalent or by sending the data over the CAN bus and catching it from that. We used Ethernet (easy to implement on our own boards and software drivers available) to speed up the download of > 50 megs of data per endurance test (sampling freq > 100hz). Most data is however from starting, setting up etc since the logger starts as soon as you turn on the power and thus useless but we decided to filter it out afterwards.

My advice:
If you build your own daq -> Don't. Use wires. If that works, use wire->wireless converter. A design decision can easily be: It is too complicated for our team so we don't.
If you have a commercial daq -> Buy a RS232 to 800/900/2400mhz band transmitter/receiver and use the default output of the daq.

[Rami]

thank you guys for your replays that really helped me a lot

[sessem13]

Now to the point of 'telemetry'. If you can download all the collected DAQ data < 2 minutes after a Endurance test you are fine with wires. Most teams either do this by RS232 or equivalent or by sending the data over the CAN bus and catching it from that. We used Ethernet (easy to implement on our own boards and software drivers available) to speed up the download of > 50 megs of data per endurance test (sampling freq > 100hz). Most data is however from starting, setting up etc since the logger starts as soon as you turn on the power and thus useless but we decided to filter it out afterwards.

I will tell u what I think
I will use a 2.4G wifi access point + 12 or 15 dB omnidirectional antenna to allow me to cover a 1Km distance. What do u think of this ??
also I don't understand some of ur words !!
what do u mean by : "download" ?? u mean that I can't monitor the data in realtime ??

[Warpspeed]

For a first year effort, how about concentrating on a really basic in car data logging system.

There will be plenty of challenge in that, and the results will be extremely useful to the rest of the team if you can get it up and working very quickly.

Later on, that could be extended to involve real time telemetry, more channels, etc...

Better to have something very simple and reliable that works to start off with, than some vast project, some of which ends up not working very well, or at all.

[PatClarke]

Rami,

Remember, the name of the event is Formula SAE or Formula Student, NOT Formula Telemetry or even Formula Electronics!

You will score very little points for a telemetry system, no matter how good it is, if the car design and execution is crap.

I think the team need to reassess their project objectives.

Pat