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Newbie question regarding sensor/bluetooth

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indy_fm

New Member
Hello my name is Marc
I registered here to ask a question about a project I'm working on.
Basically I need to come up with a transmitter and a receiver with the receiver being able to output one or more signals. The transmitter needs to be very small.

Is bluetooth the way to go? Is there anything on the market that can be bought.
I have no experience in this so any help would be greatly appreciated.

I can answer questions as well if this would help give a better understanding.

Sincerely,
Marc
 

ericgibbs

Well-Known Member
Most Helpful Member
hi Marc,
Over what range and what type of data.?
E
 

indy_fm

New Member
I need the receiver to sense the transmitter 9 to 10 feet away and then send a signal to power a light. Motion detection won't work.
Thank you for the response already.
 

Huttojb1

Member
Look at xbee devices or nrf24l01 both good for passing data.

Jason.
 

indy_fm

New Member
Thanks for all the help so far. I am looking into the products that have been recommended. I'm trying to wrap my head around how to make it work at a distance of 10 foot and closer, not farther out.
 

Huttojb1

Member
Lots of videos on YouTube.
 

Les Jones

Well-Known Member
Most Helpful Member
Hi Marc,
I am not clear about what you are trying to achieve. I get the impression that that you want the receiver to receive the signal from the transmitter when the distance between them is between zero and 10 feet but you do NOT want to detect the signal when the distance is MORE than 10 feet. Am I correct in my understanding ? In post #1 you say that you want to send one or more signals but in post #3 you say that you just want to light a lamp when the signal is received. If your requirement is as described in post #1 then what is the nature of the signals in terms of bandwidth and the maximum number of signals you need to transmit. There is a big difference in sending a simple on/off signal and 100 high definition television signals.

Les.
 

indy_fm

New Member
Hi Marc,
I am not clear about what you are trying to achieve. I get the impression that that you want the receiver to receive the signal from the transmitter when the distance between them is between zero and 10 feet but you do NOT want to detect the signal when the distance is MORE than 10 feet. Am I correct in my understanding ? In post #1 you say that you want to send one or more signals but in post #3 you say that you just want to light a lamp when the signal is received. If your requirement is as described in post #1 then what is the nature of the signals in terms of bandwidth and the maximum number of signals you need to transmit. There is a big difference in sending a simple on/off signal and 100 high definition television signals.

Les.
Correct. I want to detect the signal when it is 10 feet away or less. When the receiver detects the signal, I want it to send a signal that would power on a light, buzzer or whatever and possibly both. I also would like the receiver to pick up more than 1 transmitter but does not need to differentiate between any of them. One in proximity would accomplish the same as 3 in proximity. Is this what you mean by bandwith? Sorry, I'm not versed in this stuff.
 

Les Jones

Well-Known Member
Most Helpful Member
Hi Marc,
It is not possible to accurately determine the distance between the transmitter and receiver purely based on signal strength. It would be theoretically possible to measure the distance by measuring time. this would require a transmitter and receiver at both ends of the link. One end would transmit a short pulse. the receiver that end of the link would see that pulse and start timing. The receiver at the other end would receive the signal and trigger it's transmitter to resend the pulse. The end that originally sent the pulse could measure the time between the pulse that it sent and the one received. This time would be twice the time for the signal to travel between the two units plus the delay at the remote end in re transmitting the received pulse. For 10 feet (This is almost the same as 3 metres. which is easier to use for the calculation.) the time would be 6 metres divided by the speed of radio waves (300000000 metres per second.) So the time to be measured would be 20 nS plus the delay for re transmission of the pulse. It would mot be practical to use this method to measure such a short distance.

Les.
 
Last edited:

indy_fm

New Member
Thanks Les.
I think I get what you are saying. Because of having to bounce information back and forth to determine distance and the trigger point, It would not be feasible because by the time the relay was triggered, the object could have closed all 10 feet. Correct?

ericgibbs,
I have not looked at that technology yet. Is it for indoor use only? Can it be used in a mobile situation?
 

Huttojb1

Member
Could you use GPS. Both controls have GPS Attached. One controller constantly sends its GPS Position, other receives and determines distance away????

Jason
 

MikeMl

Well-Known Member
Most Helpful Member
Ranging implies measuring time-of-flight of a signal. Time-of-flight of ultra-sound (3ms/m) is a lot easier to deal with than time-of-flight of RF (3.3ns/m).
 

indy_fm

New Member
Could you use GPS. Both controls have GPS Attached. One controller constantly sends its GPS Position, other receives and determines distance away????

Jason
Not sure. Is there a delay up and down or is gps realtime? It is critical that this has no or as little lag as possible.
 

Pommie

Well-Known Member
Most Helpful Member
If you tell us what you are trying to achieve rather than how you think you can achieve it then we may be able to help.

Mike.
 

indy_fm

New Member
If you tell us what you are trying to achieve rather than how you think you can achieve it then we may be able to help.

Mike.
Mike,
I want a stationary object to pick up the presence of a mobile object when it comes within 10 feet of it. I then want the stationary object to light up or buzz as a result. I want the stationary object to sense the object or objects regardless of what direction they are coming from. Does this help?
 
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