Single chip transmitters?

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beamin

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I'm trying to make a simple transmitter beacon in VHF/UHF range. The goal is to make something small and battery powered for experimenting with antennas. I have an SDRPlay and want to make directional receive antennas and see if I can go and play hide and seek with the transmitters.
There are so many I can't figure out what would be suited for this application. Ideally I would want it to make a tone but a CW might work. For making the antenna a practical size I was thinking 455 900mhz. They dont put out much power so I'm not to worried about making interference, but I also dont want to put it in a crowded area of the spectrum.

I just discovered these at mouser.com but am not sure which ones to order. They are cheap enough where I was going to order 10 different chips. If some dont work its not a big deal at 1.50usd each.
 

beamin

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Another thing: I can only do through hole stuff and since these are all surface mount it has to be big enough to flip up side down and solder wires to. Some chips are 3x3mm! No way am I going to be able to solder to those leads!
 

RFI-EMI-GUY

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I have attached details of a high performance rocket recovery beacon I designed. It utilizes the LINX TXM433LR long range ISM module and a PICAXE -08 Microchip with the Revolution Education boot loader.

The file for my program is in the zip file. You will need the programming editor (link below) to run my file in emulation and/or to make changes.

Basically the program is as follows. There are two output pins from the PICAXE-08 PIC chip that connect to the TXM433LR (433.920 MHz) module and provide :

1) Transmit enable (a long duration HIGH pulse to PDN Pin from PICAXE-08 pin 6) and
2) Transmit (a short LOW pulse to DATA pin from PICAXE-08 pin 7).

These are pulsed to enable the transmitter in a CW mode to act as a long range beacon to be received on a TeleVilt UHF wildlife tracking receiver.

The program has two input pins (PICAXE pins 3 and 4) which when toggled LOW make changes to the CW by modulating with tones so that one can determine if a parachute has deployed plus another status input.

If you run it on the program editor, you can see the outputs pulse and you can toggle the input pins.

As far as the TXM433LR, it is probably one of those small chips you mentioned. I was able to buy (at a small premium) the same chip mounted on a daughter board with antenna and edge connector. This made wiring to a through lead board, much easier. The module requires a 750 ohm resistor for setting power level and 10 ohm resistor and 10uf capacitor to filter the power pin. I recommend the LR version modules as they are much more frequency stable than the cheaper versions. The TX enable (PDN) pin stabilizes the module by a high state activating the oscillator before transmission (DATA pin LOW) and saves power when low..

A word about the -08 Microchip. You must ground or pull up unused pins using a 10K resistor or the operation will be erratic due to static electricity. The onboard 4 MHz clock is used for timing.

The entire beacon will run a very long time on a CR123 3 volt lithium battery. The PIC will run fine on 3V, but requires 4.5 to program it. Conversely, the TXM433LR likes 3V and does not like 4.5V. So when programming, use one of the inexpensive programming/prototype boards.

I ended up making a fixture using a breadboard to program and test the entire beacon. It requires me to unplug the RF module when programming and adding a AA battery to satisfy the programming voltage. Pretty clunky, but it worked. I added 2 LED's to show TX enable and TX pin status.

The modulation is basically on off keying. When the program generates a tone it is by a fast square wave (LOW) on the TX (DATA) pin.

Let me know if you have any problems getting the program to run. It has been a long while since I worked on this project,

Revolution Education - Educational Kits, Robots and Microcontroller Systems

PICAXE Programming Editor (BAS805) - Software - PICAXE
 

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beamin

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I have attached details of a high performance rocket recovery beacon I designed. It utilizes the LINX TXM433LR long range ISM module and a PICAXE -08 Microchip with the Revolution Education boot loader.

The file for my program is in the zip file. You will need the programming editor (link below) to run my file in emulation and/or to make changes.

Basically the program is as follows. There are two output pins from the PICAXE-08 PIC chip that connect to the TXM433LR (433.920 MHz) module and provide :

1) Transmit enable (a long duration HIGH pulse to PDN Pin from PICAXE-08 pin 6) and
2) Transmit (a short LOW pulse to DATA pin from PICAXE-08 pin 7).

These are pulsed to enable the transmitter in a CW mode to act as a long range beacon to be received on a TeleVilt UHF wildlife tracking receiver.

The program has two input pins (PICAXE pins 3 and 4) which when toggled LOW make changes to the CW by modulating with tones so that one can determine if a parachute has deployed plus another status input.

If you run it on the program editor, you can see the outputs pulse and you can toggle the input pins.

As far as the TXM433LR, it is probably one of those small chips you mentioned. I was able to buy (at a small premium) the same chip mounted on a daughter board with antenna and edge connector. This made wiring to a through lead board, much easier. The module requires a 750 ohm resistor for setting power level and 10 ohm resistor and 10uf capacitor to filter the power pin. I recommend the LR version modules as they are much more frequency stable than the cheaper versions. The TX enable (PDN) pin stabilizes the module by a high state activating the oscillator before transmission (DATA pin LOW) and saves power when low..

A word about the -08 Microchip. You must ground or pull up unused pins using a 10K resistor or the operation will be erratic due to static electricity. The onboard 4 MHz clock is used for timing.

The entire beacon will run a very long time on a CR123 3 volt lithium battery. The PIC will run fine on 3V, but requires 4.5 to program it. Conversely, the TXM433LR likes 3V and does not like 4.5V. So when programming, use one of the inexpensive programming/prototype boards.

I ended up making a fixture using a breadboard to program and test the entire beacon. It requires me to unplug the RF module when programming and adding a AA battery to satisfy the programming voltage. Pretty clunky, but it worked. I added 2 LED's to show TX enable and TX pin status.

The modulation is basically on off keying. When the program generates a tone it is by a fast square wave (LOW) on the TX (DATA) pin.

Let me know if you have any problems getting the program to run. It has been a long while since I worked on this project,

Revolution Education - Educational Kits, Robots and Microcontroller Systems

PICAXE Programming Editor (BAS805) - Software - PICAXE
I do have a pic programmer from vellman, but it wants a serial connector output from the computer. I do have a serial to usb converter lead, but dont know if that will work. I also have a vellman relay board where you can remove and program the pic from usb, but the software was really pricey so it sit collecting dust until I can figure out how to program the chip.

Thanks again, Im going to see about ordering those chips, I lost soooo many model rockets as a kid, I think all of them actually.


EDIT:

Which products am I looking for specificly from that site? PICAXE-08 PIC chip
and TXM433LR transmitter chip? or is the transmitter chip something mouser would sell?
 
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RFI-EMI-GUY

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I do have a pic programmer from vellman, but it wants a serial connector output from the computer. I do have a serial to usb converter lead, but dont know if that will work. I also have a vellman relay board where you can remove and program the pic from usb, but the software was really pricey so it sit collecting dust until I can figure out how to program the chip.

Thanks again, Im going to see about ordering those chips, I lost soooo many model rockets as a kid, I think all of them actually.


EDIT:

Which products am I looking for specificly from that site? PICAXE-08 PIC chip
and TXM433LR transmitter chip? or is the transmitter chip something mouser would sell?
The TXM433LR is available from Digikey I am certain. It requires no programming, just hook it up. I bought some from another small vendor which were already soldered to a small board, had a wire antenna and edge pins spaced to mate with a proto or bread board. If you do a Google search for that product number, maybe there are still some available. It saves the hassle of board layout and soldering.

The PICAXE-08 is available from Revolution Education in the UK as well as sellers in the US. There are programmer/proto boards available in seriel and USB. Very inexpensive stuff. The PICAXE bootloader requires only the programming hardware interface and the programming editor (free). You can actually program the chip directly with just a PC and some seriel wire hook up. I did my project as a complete neophyte to programming.

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beamin

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Cool! I have all that stuff downloaded and will be ordering the chip once I figure out some other things to include with the digikey order.

With the standard tip on the hayco soldering iron, soldering to those little pins on the ic to wire wrap wire should be doable as a dead bug configuration?
 

RFI-EMI-GUY

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Cool! I have all that stuff downloaded and will be ordering the chip once I figure out some other things to include with the digikey order.

With the standard tip on the hayco soldering iron, soldering to those little pins on the ic to wire wrap wire should be doable as a dead bug configuration?
It will probably work. But there probably should be ground plane under the chip.

What you might try is get a small chunk of blank PC board, solder side up, mark the 8 pins. Note the Data, LADJ/VCC, PDN VCC and antenna pins and make islands around those pins using an X-Acto knife blade. Then solder everything down. That way the ground pads and the chip body will have a good RF ground plane. That would probably be best and most secure.

My very first prototype I built that way and put the PC board on top of a Radio Shack proto board and soldered the leads from the module and the IC sockets and other parts to the prototype board. Digikey sells Keystone CR123 battery holders with a retaining clip. I mounted one of those to the proto board. The whole thing is quite compact.

My neighbor launched these in his L3 rockets and they took quite a bit of abuse.

I built an earlier prototype using 556 dual timer and the parts count and hassle of design was too much. The PICAXE-08 is the way to go for a simple beacon.

If you are really into programming and RF design, then the TI msp430 and system on a chip CC430 RF core is the direction to go further. I haven't done much more than attend a class on how to program those. I don't think it was hard, just a lot of new stuff for me. You can make a single chip beacon and have more modulation options. You will have to mess with some small inductors and capacitors external to the chip to make a complete transmitter.
 
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beamin

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It will probably work. But there probably should be ground plane under the chip.

What you might try is get a small chunk of blank PC board, solder side up, mark the 8 pins. Note the Data, LADJ/VCC, PDN VCC and antenna pins and make islands around those pins using an X-Acto knife blade. Then solder everything down. That way the ground pads and the chip body will have a good RF ground plane. That would probably be best and most secure.

My very first prototype I built that way and put the PC board on top of a Radio Shack proto board and soldered the leads from the module and the IC sockets and other parts to the prototype board. Digikey sells Keystone CR123 battery holders with a retaining clip. I mounted one of those to the proto board. The whole thing is quite compact.

My neighbor launched these in his L3 rockets and they took quite a bit of abuse.

I built an earlier prototype using 556 dual timer and the parts count and hassle of design was too much. The PICAXE-08 is the way to go for a simple beacon.

If you are really into programming and RF design, then the TI msp430 and system on a chip CC430 RF core is the direction to go further. I haven't done much more than attend a class on how to program those. I don't think it was hard, just a lot of new stuff for me. You can make a single chip beacon and have more modulation options. You will have to mess with some small inductors and capacitors external to the chip to make a complete transmitter.
I'm fairly new to all this, I messed around as a kid, but didn't get back into the hobby until last summer. I went to college for chemistry not EE so everything I learned is off the internet. Programing can be tedious for me; I'm just starting to make arduino stuff, mainly from copy and paste then modifying that. I learn quickly though.

Do you have any pictures? How did you mount the chip to the copper? I thought that chip had recessed leads. So from the copper board you ran leads to an ic socket?
 

RFI-EMI-GUY

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I'm fairly new to all this, I messed around as a kid, but didn't get back into the hobby until last summer. I went to college for chemistry not EE so everything I learned is off the internet. Programing can be tedious for me; I'm just starting to make arduino stuff, mainly from copy and paste then modifying that. I learn quickly though.

Do you have any pictures? How did you mount the chip to the copper? I thought that chip had recessed leads. So from the copper board you ran leads to an ic socket?

Calling them pins is sort of a misnomer. They are little recessed pockets of tinned metal awaiting a wave soldering process.

Make a small square of single side copper PC board just larger than the TXM433LR module.

Cut little islands on the PC board for the pins that are other than ground. Then flow solder from the PC board copper to each pin. Solder short flying leads from each pin plus the ground plane copper.

Someone used to sell a hollow drill bit that would drill a through lead hole and carve a perfect circle in the copper for dead bug prototyping. They may be too large for this package. If so, the Exact opposite knife will have to do.

When I mentioned IC socket, it was for the PICAXE-08. You will want it socketed for reprogramming. The RF board you create will be placed onto a section of Perf Board. The stuff from Radio Shack with copper runners.

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beamin

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I cant for the life of me find that chip on any board. The size is fine for soldering, I have actually managed to solder a sot23 package, but that was something that I wouldn't want to do again, not without a break out board, I soldered to four of six pins on a perf board. Maybe if I had a microscope that would have been less tedious. What company did you get them from?

EDIT I just read your post backwards. You ment a socket for the pic not the rf chip.
 
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RFI-EMI-GUY

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I cant for the life of me find that chip on any board. The size is fine for soldering, I have actually managed to solder a sot23 package, but that was something that I wouldn't want to do again, not without a break out board, I soldered to four of six pins on a perf board. Maybe if I had a microscope that would have been less tedious. What company did you get them from?

EDIT I just read your post backwards. You ment a socket for the pic not the rf chip.
I got them from a small company in Colorado. REMCOM or something like that. It seems he is no longer in business. I found a schematic with his company name on Google images .

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RFI-EMI-GUY

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I got them from a small company in Colorado. REMCOM or something like that. It seems he is no longer in business. I found a schematic with his company name on Google images .

Sent from my SM-T350 using Tapatalk
It was Reynolds Electronics , Owner Brice Reynolds. The website seems to be down. The Wayback Machine has shots of the website so maybe you can find a phone number.

http://www.rentron.com/index.html

This article may have suggestions for other sources of demo boards.

A Wirless Throttle for HO Scale Train Control

Contact Info for RENTRON

Reynolds Electronics. Canon City, Co. 81212 http://www.rentron.com. Tel: (719) 269-3469 Fax: (719) 276-2853 e-mail:webmaster@rentron.com.
 
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