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Humanoido
10-22-2011, 01:49 PM
with the following requirements:
Simple DIY connects to Propeller chip
Very light weight
Tiny physical size
A circuit with almost no parts
Uses common easy to find parts
Range about 10 or 12 feet
Simple software
The purpose is to connect the transmitter to a Propeller chip and send it up, by rocket, into Micro Space (about 10 feet high). During this time, the Propeller will read a Parallax accelerometer and feed the telemetry info to transmitter. The transmitter will send as much continuous data as possible in real time during a two second flight. The receiver is connected to another Propeller chip and holds the data, then stores the data after flight for later playback.

Mike G
10-22-2011, 01:57 PM
Why not just store the data in RAM on the Prop chip that goes up in the rocket.

Humanoido
10-22-2011, 02:26 PM
Why not just store the data in RAM on the Prop chip that goes up in the rocket.There is a version being developed that does just that, however for this experiment the rocket is treated as non-recoverable.

ChrisGadd
10-22-2011, 02:55 PM
What kind of bandwidth are you looking for? The prop itself is capable of producing a 120MHz signal, shouldn't need much of an amplifier to transmit 12 feet, a 1/4 wavelength antenna is about 2 feet at 120MHz, use simple on/off keying ... I think it could be done.

Mike Green
10-22-2011, 03:03 PM
Over that sort of range, I'd use IR. On the Prop end, you'd just need two LEDs (to get a broad "beam") along with their series resistors to limit total current to about 30mA. A cog counter could be used to make the 38KHz carrier which you could switch on and off. You could use a Simple_Serial object (slightly modified) to send the data. Rather than controlling OUTA, it would control DIRA to switch the I/O pin from output to input. On the launchpad end, you'd have a standard modulated IR detector hooked up to another Prop. You'd need to keep the Baud slow (maybe 1200 or 2400 Baud) and use a lot of error checking and redundancy in the data.

Ray0665
10-22-2011, 04:35 PM
Check out my Sure Electronics GP-GC010v1 / CY2196R 433Mhz driver/demo in the OBEX the transceivers are available for about $10 each

Humanoido
10-23-2011, 08:16 AM
What kind of bandwidth are you looking for? The prop itself is capable of producing a 120MHz signal, shouldn't need much of an amplifier to transmit 12 feet, a 1/4 wavelength antenna is about 2 feet at 120MHz, use simple on/off keying ... I think it could be done.Another good idea. I tried searching for the link but the search engine didn't bring it up. Any idea where the propeller to transmit forum link is located?

Humanoido
10-23-2011, 08:23 AM
Over that sort of range, I'd use IR. On the Prop end, you'd just need two LEDs (to get a broad "beam") along with their series resistors to limit total current to about 30mA. A cog counter could be used to make the 38KHz carrier which you could switch on and off. You could use a Simple_Serial object (slightly modified) to send the data. Rather than controlling OUTA, it would control DIRA to switch the I/O pin from output to input. On the launchpad end, you'd have a standard modulated IR detector hooked up to another Prop. You'd need to keep the Baud slow (maybe 1200 or 2400 Baud) and use a lot of error checking and redundancy in the data.This is a very good idea. It sounds like a Penguin robot program I made some time ago that does exactly this function. Too bad I can't directly convert BS2px PBASIC code into Spin. However, as I recall, the range of the on-board IR transmitter receiver was around 6 or 7-feet.

Humanoido
10-23-2011, 08:29 AM
Check out my Sure Electronics GP-GC010v1 / CY2196R 433Mhz driver/demo in the OBEX the transceivers are available for about $10 each Good idea. I wonder if the transceiver and two boards would end up totaling too much weight for the rocket. The rocket payload weight expectedly cannot exceed approximately one Propeller chip, a tiny cell battery and a few tiny components.

This is a demo of the Sure Electronics GP-GC010v1 433Mhz Transceiver (CY2196R) It is a block Send/Receive with checksum, all in Spin. Two Transceivers and two propeller boards are required to use these modules. Board A creates, sends, receives and displays a packet. Board B retransmits any packet it receives with a small modification for demo purposes.

Ray0665
10-23-2011, 05:25 PM
The demo needed two setups (obviously) because I implemented a master send, slave echo, master receive, kind of approach.
The rocket/ground setup only needs a send on one side and receive on the other (and the transceiver module is quite small).

The heart of my demo, is/are the two Block send /receive routines augmented with a few utility routines.

As setup here it is kinda slow at only 19.2 K baud. The data on these modules is very sparse but it does mention a faster baud rate setting but I do not know how to set that. Everything I learned about these modules was found by experimentation.

Ray0665
10-23-2011, 05:50 PM
Here is the data sheet on the module such as it is
http://www.sure-electronics.net/rf,audio/GP-GC010.pdf

***** Use the wiring diagram and pin outs from my demo module not from the data sheet ****

To clarify my comment about being slow --
I think at 19200 baud you can get 37 packets per second out of this setup
19200 baud / (8 bits per byte * 64 bytes) ~ 37 packets per second

Hope this helps


Post edit
I have attached the stripped packet send/receive modules if you want them

Post edit 2
Updated packet send/receive to remove unused led module and add keep alive variable

Duane Degn
10-24-2011, 05:47 PM
Humanoido,

These (http://www.ebay.com/itm/NRF24L01-Wireless-Transceiver-Module-2-4GHz-ISM-band-/320696838110?pt=UK_Computing_DesktopComponents_RL&hash=item4aab0567de) will provide two way communication (up to 2Mbps). They cost less than $7 each.

I wrote a driver for the Propeller (http://forums.parallax.com/showthread.php?130707-Looking-for-Faster-Objects-for-Nordic-Wireless-Modules-nRF24L01-and-nRF2401A/page2).

Duane

Mike Green
10-24-2011, 05:58 PM
About using IR ... The Prop can handle higher I/O pin current loads than the Stamps. The Stamp pins are rated around 25mA. The Propeller pins can handle up to about 40mA. Given that a standard TV remote control can work over distances on the order of 10-12 feet, you ought to be able to get a small amount of data over that distance as well.

Humanoido
10-27-2011, 03:16 PM
Thanks everyone! Lots of excellent options here!

Cluso99
10-27-2011, 10:21 PM
Humanoido: Dr_Acula uses radio modules for comms between his cpm modules and they are very reliable. Perhaps you could PM him as he may not read this thread.

dr hydra
10-31-2011, 03:15 PM
Using IR...can you use the full duplex object to send information between two propeller..I am thinking of a distance of about 5 to 6 feet and only one way communcaiton (client/server)... Would I need to modify the spin/PASM objects...Baud 38400...right