Hi,
I am working out pros/cons about various means to measure distances to objects. I found a lot of information regarding ultrasonic and laser-diode-based measurements.
Now, I came accross a sensor called "RAD-MOD" from Hygrosens.
It's a motion sensor, but the data-sheet also states that it is possible to measure distances.
How can I (in principle) use this sensor, together with an Arduino to measure the distance to an object? Or is such a sensor totally unusable therefore?
Regards,
It's a Doppler unit - I don't see where it says you can get range info from it.
[edit]It's got a digital output, with a basic sensitivity setting via pot - no range data[/edit]
Ah, sorry I posted the wrong model (I meant this one: http://www.produktinfo.conrad.com/datenblaetter/500000-524999/502374-da-01-en-RADAR_SENSOR_RSM_3650.pdf).
Anyway, this uses Dopplereffect too. So it can only detect movement from/to the sensor? And if I get it right, it cannot calculate the distance, but only the speed the object is moving towards the sensor?
That's the same as the first, but without the digital output - it simply gives you the raw Doppler AF signal.
Simple Doppler units like this transmit continuously on a single frequency, so range information is not possible.
All that can vary is signal strength, which could be a return from a large object far away, or a small object nearby.
Thank you. I think I'll stay with the ultrasonic sensors ;).
For reference, see the following article under "CW (continuous Wave)"
Hello,
anyone have installed this device successfull to an arduino board and have some code to get the signals??
cheers,
andreas
anyone have installed this device
Which one?
I'd be careful with the IF only version - the output swings down as low as -300mV
Thanks for your quick reply.
I want to measure the speed of an object. So i dont know if i can use the one which output the digital signal which is prefiltered?!
Maybe speed measure is not really possible with the arduino because of there is no documented project with this goal?!
Or no one need have need it so far?
best regards
Maybe speed measure is not really possible with the arduino
It's not the adruino that is doing the speed measurement it is the Doppler module.
because of there is no documented project with this goal
Here is a a piece of sage advice, the internet is not the depositary of all human knowledge, capability or things made. I know you might think so especially if you are young.
Thanks grumpy for this GREAT advice - But no one is interested in it... So if you have to say something usefull for the members reply it...
So if the arduino would be able by itself to measure things like speed why should i post it in the interfaceing section?! Doh.
Really? The Doppler module can do this for me? Great-thats the reason why i started here...
Start again reading my post! I just recognized there is no project with the aim of measure speed of an object, but there are tons of projects about how to measure the distance - again, why do you post a reply that doesnt help anyone out there?!
Okay just for you i rewrite my sentence:
'Maybe speed measure with this interface/module isnt possible with arduino because of a special/exotic output - i dont know anything about the output!'
OK rephrasing your question gets you another answer.
There is nothing in the interface of a doppler module that prevents you from reading it's output with an arduino.
Now what doppler module are you using? Have you a link to the data sheet?
Have you a real question you want to ask about it?
If you read the datasheet you linked in the other thread, they mention that the size/distance of the object relative to the amplitude, +- 300mV is mentioned, and the speed is relative to the frequency with 40Hz=1km/h. They also mention further you to expect frequencies from 20-900 Hz.
While all this isn't really a data sheet, it gives you some indication what to expect. For a more complete data sheet and some sample circuits to interface with a microprocessor, they ask you to contact them.
Korman
Rephrasing sounds good...
The Datasheet is linked in this thread some post above:
http://shop.hygrosens.com/en/acma-acma/acma/Radar-movement-alarm-unit.html
This one is combined with an circuit for movement detection where its possible to set the sensitivity and as groove says the output is digital?!
The module itself is documented here http://www.produktinfo.conrad.com/datenblaetter/500000-524999/502374-da-01-en-RADAR_SENSOR_RSM_3650.pdf (also posted before in this thread).
Like groove asked me to get the more information offerd in the datasheet i have asked the reseller to send them - until now no answer.
Real question? Is there anyone who can help me set up a circuit with this module to get a working speed measure powered by arduino.
Im not an advanced not even an semi electrician but i can understand working circuits and the code and modify it to my needs and thats the reason why i have first asked if there is someone who used this module before.
And in my opinion this forum is the right place to start - please correct me if the members have to be genius and pro electrican, its hard enough for me to feel like a rookie when i start to ask my question here... 
Thanks.
@Korman - i asked them this morning for the additional papers.
As soon as i get them i will be back with more information!
The digital output version (as far as I can tell) is simple motion/no-motion, a bit like a PIR, but with some form of pot-driven sensitivity control.
You need to be able detect and measure the frequency using the analogue IF-only version.
As noted, you'll need to offset the signal so it is 0-600mV, and measure the frequency.
Make sure you have good supply frequency rejection, or you'll end up with lots of objects moving at about 1.13km/h (or 1.36km/h if you're Atlantically-challenged) ;D
BTW, I'm with Grumpy Mike on the "the interweb is not the sole repository" thing.
What were those things we used to read called?
Began with a "B"...ooo, it's on the tip of my tongue... 
Thanks Groove...
as i ordered my first arduino board i bought several Books about arduino.
I´ve done some of the basic circuits and beginner projects and ended up
with the idea of measure the speed...
Sure internet iss not the repository for anything... But its a place where other people can point you to the right offline repository?! Isnt it?
I have no one around me who is interested in arduino or other microcontroller and/or any kind of circuits so the first place to start is for me the magic interweb - and iam sure you and even grumpy mike start here too - maybe not for electric , microcontroller questions or something like this - but if you need some other information like how to cook a turkey or how to troubleshoot something else - maybe the advice is too 'buy you a cook book' f.e.. But sometimes a friendly interweb people will just answer your question and you are happy without get pointed to offline media... I m sure you know what i mean...
I dont want that someone do the work for me, but i want to get
some help getting started, maybe with a tip for the right books.
Cheers
iam sure you and even grumpy mike start here too
No, they were still chiselling rocks when I started.
Just a point that, as mentioned, this module is not designed for measuring speed. It may turn out you can do it but then it might turn out that it is not possible with this module.
You haven't said what range of speeds you are interested in. That will have a great impact on the design of your amplifier and frequency measuring circuit / technique. The quoted 44Hz is for a speed of 0.28 meters per second.