Serin from radar speed sensor.

[Shafto]

There's a bicycle race in town that a friend of mine is competing in, a fundraiser, and for my contribution I want to build something for the race. A radar speed sensor that will post the speeds on a 7 segment LED display down the straight stretch.

The specs for the radar speed sensor that I am ordering are here: http://www.stalkerradar.com/stalker-speed-sensor/stationary-speed-sensor/Stationary Speed Sensor specification.pdf

It sends the speed data out as serial data. I've never played with sending or receiving serial data before, and I just have a few simple questions before I start off.

Is the serial data from the speed sensor as simple as sending a number 0-255, which is then converted to 0-200MPH? I'm thinking that it must not be that simple, but I'm unsure. I want to use KPH, so the range for that is 0-321, which would mean I would have have a resolution less than 1KPH, which is fine, it just leads me to believe it must be more complicated than that.

Why would this unit even have a MPH or KPH setting? wouldn't the serial data all just be the same raw numbers that you convert within the the unit receiving the information? I don't even know how you would change these settings, there's no information on how that is done. I know I should probably be asking the manufacturer these questions, and I will, just thought I would put them up here too.

Thanks for all the help.

 

[BCJKiwi]

The referenced spec sheet is not very helpful.

One would have expected the data transmitted to match the data type set - i.e. if set in kph, transmit kph.

Since you probably want 10/ths of Kph any way - looks more techo! - then a word variable would probably be needed (and there could be more data coming along with the raw speed info).

Suggest you email them or call the 1-800 number since they won't let you download the manual without having a logon (Duh!), and, there is insufficient info to make an informed decision from the spec sheet alone.

 

[Dippy]

Unless you can find info elswhere on Nerdynet (come on eclectic!) I agree with BCJ - email them.
They'll know a tad more about their product than anyone here.

"Is the serial data from the speed sensor as simple as sending a number 0-255, which is then converted to 0-200MPH?"
- dunno.
Why not try it? Scared? It won't explode

As the device is configurable in KPH too (according to the Data Sheet) then it would be tricky to send a value of 320 in a byte.

"wouldn't the serial data all just be the same raw numbers that you convert within the the unit receiving the information?"
- what do you mean by "raw"?
I think I know what you mean, but many devices are designed for ease of use. Many numpties couldn't use simple maths to work it out.

Are there switches on the unit to select speed units etc?

Have you experimented to see how many bytes per data block is coming out?
Or 'scoped it?
Sticking a 'scope on it would give the solution in a couple of seconds.
Even trying a few Serins would just take a few minutes...
Why the reluctance to have a go???

PS How much do these things cost and where do you get them?

 

[Dippy]

Actually, this product interests me so I might email them. I'm glad you posted.
(I spent ages doing FFT on a dsPIC and even though it worked OK the resolution wasn't brilliant).

I notice from the brochure that it can do direction sensing.
It also says "Selectable output protocols and data formats".

I think you will need to investigate further.
If it can do direction sensing then it may chuck out the data as a twos-complement word.
Or something even more convoluted.
But whatever, I'm sure the conversion is easy. (well, twos comp is anyway).

 

[Shafto]

Thanks guys, I actually don't have the unit yet, in the process of getting one, but it hasn't exactly been easy. So far price looks like ~$125CAD. I'm working with a partner on this project and he has been the one dealing with these guys. I'll talk to him tomorrow and get some more information.

Like I say I just haven't played with sending serial data around before, just wanted to get a head start on it. Maybe it sends a byte of data per digit?

I'll keep updating as I go...

 

[Dippy]

Re: Price. Thanks. Looks pretty good value.

"Maybe it sends a byte of data per digit?"
- maybe... maybe selectable..

Let us know when you find out.

I'd like to know:-
1. the time from power-up to valid data o/p (for duty cycling if battery powered).
2. Response time from being polled.

And you realise that you may have to do some trig if speed measured off-axis?
So, if the beam is 12o spread and you measure at 30o to target then you may have to do some serious number twiddling - esp if close to target.
And the 12o is the 3db value so at close range it'll be (effectively) wider than that.
Mmmm... cue head scratching.

But hey, thats the fun part

I've only ever used Microwave-Solutions modules, which are a bare module. Disadvantage: you have to do the hard work. Advantage: <<millisecond warm up time.

 

[hippy]

The comment in the datasheet under "leading zero character" suggests that there are at least some modes which send data in a character by character format rather than as binary units so that should be relatively straight forward to interface to.

The best thing I find is to hook a serial outputting device up to a PC running a terminal emulator to see what is coming out ( using MAX232 or other inversion if necessary ) then write the PICAXE code to suit the data. Using a PICAXE to try and determine what the data is is usually more difficult.