Ti-83 plus wireless link circuit help

[audioguru]

Do I think a toy transmitter will transmit very far to a toy passive crystal radio when their coils have a capacitor across them with a value spread of 10:1??
An good inexpensive set of 433MHz transmitter and real radio would be much, much better.

 

[DigiTan]

Could you modify the current design for better performance (maybe starting with the reciever)? This looks like a cool RF project, and I'm not really learning much with these store-bought 433MHz's.

 

[hyedenny]

Hi
You can do it with a pic (or basic stamp) and a transmitter chip from LINX which has a range of over 3000ft. Your TOTAL parts count is 6 for the whole thing. And the cost, if you use the pic, will be less than 15 dollars.

https://www.linxtechnologies.com/

 

[hyedenny]

OR...... you could use an rfPIC (like the rfPIC12f675) which is a microcontroller and a transmitter all in one! Ive never used one, but I want to soon!

 

[Nigel Goodwin]

OR...... you could use an rfPIC (like the rfPIC12f675) which is a microcontroller and a transmitter all in one! Ive never used one, but I want to soon!

I suggest you study the datasheet - it's not easy or cheap to use!.

 

[DigiTan]

Yes, I have the AVR equivalent of those chips-- the AT86RF401. But I don't think these modules are really advancing my understanding of RF circuit engineering. I'd prefer to do it with discretes if possible first--like audio's RF voice transmitters.

 

[Nigel Goodwin]

Yes, I have the AVR equivalent of those chips-- the AT86RF401. But I don't think these modules are really advancing my understanding of RF circuit engineering. I'd prefer to do it with discretes if possible first--like audio's RF voice transmitters.

The licence free radio modules are just that, 'licence free', if you build your own presumably you will have to either get a licence for them (probably impossible?) or submit them for licence free testing (probably EXTREMELY expensive).

 

[DigiTan]

If it's on the AM broadcast band, longwave (within only 160 to 190 kHz), or CB band (within 26.96 to 27.28 MHz we're allowed 100mW from the FCC part 15 rules. So how about it? Can you guys help me out?

 

[DigiTan]

I take it from the 3-day silence no one can help.

[edit]

If it helps, I'm just curious about:

1. Will the posted design work? At all?
2. If not, what's okay and what isn't?
3. Shouldn't the transmitter/reciever be isolated somehow? Like with a duplexer?

 

[DigiTan]

Why won't anybody help me? :cry:

 

[Nigel Goodwin]

Why won't anybody help me? :cry:

Why don't you build it and try it?.

 

[DigiTan]

I'm having a lot of grade trouble in my EE major, so I don't get to build much anymore. Actually, I've been thinking of giving up on my degree. :cry: There aren't a lot of parts though, so I guess I could do it as long as I can get the coils right. When it says the coils are [.27-.3], that's in millihenrys right?

 

[arigold125]

wireless

How would i use a pic and a transmitter chip from LINX??
is that the easiest way to do this?? I,unlike digitan, am most intrested in building the simplest, cheapest wireless transmitter possible. I only need it to go a couple of feet and allow me to send files back and forth with a pair of TI calculators.

 

[hyedenny]

hi arigold
Try looking at www.rentron.com for some good ideas.

 

[arigold125]

wireless

ok but i dont have much experience doing this sort of stuff, so i really need something that is fully planned out

 

[DigiTan]

Re: wireless

How would i use a pic and a transmitter chip from LINX??
is that the easiest way to do this?? I,unlike digitan, am most intrested in building the simplest, cheapest wireless transmitter possible.

LINX mods only support a data rate of ~5000bps, which is only about half the minimum rate used by TI-OS--or 1/4 if it's a 68k model. That limit's compounded by the fact that you're encoding for 2 bi-directional lines instead of one, and since TI-OS and all third party software use the DBUS protocol, you need to encode both lines at all times to support handshaking. That's a lot of encoding to do at only 4800bps.

The posted schematic might not have that problem, but since it doesn't amplify the recieved signal, I doubt it can sink enough current for the TI calc to read. I was hoping Nigel, audio or the others could recommend something; but so far I've gotten more questions than answers.

 

[mramos1]

Re: wireless

How would i use a pic and a transmitter chip from LINX??
is that the easiest way to do this?? I,unlike digitan, am most intrested in building the simplest, cheapest wireless transmitter possible. I only need it to go a couple of feet and allow me to send files back and forth with a pair of TI calculators.

You are not cheating are you? Or helping someone in class? Send data between calculators...

Someone mentioned radiotronics parts in another topic, they were low cost ($4 each I think they said), you can make your own antenna (rather than buy one). Maybe hit the radiotronix website and see what they have.

Is the output from the TI RS232 TTL levels? I will have to go back and read the posts again.

 

[DigiTan]

The outputs and input for TIs are at TTL levels, and each use 1 bipolar transistor for logic switching. For inputs, they use diodes and pull up resistors to read the current state of the lines. The more detailed description is on Ticalc's Technical Information Archive titled "All about the 86 Link Port." (I couldn't direct-link).


Anyway, the diodes are why I wanted to ask audio and Nigel about the reciever. I'm pretty sure a crystal radio couldn't draw enough current through the diodes to switch the inputs from high (idle) to low. But if no one wants to help, I say screw 'em all; maybe some CW transeiver circuits would do the job. It's just a real pain encoding for 2 bi-directional lines at once. It would have to be done without a duplexer as well.

 

[Nigel Goodwin]

Anyway, the diodes are why I wanted to ask audio and Nigel about the reciever. I'm pretty sure a crystal radio couldn't draw enough current through the diodes to switch the inputs from high (idle) to low.

I don't see why not?, a CMOS input requires almost no current at all - I'm just dubious about a crystal receiver working at all?.

Basically, as I said before, you need to build it and try - no good asking here, as no one has built it.

 

[arigold125]

TI wireless

I finally found this-
**broken link removed**

I'd rather not have to build it though. If anyone is willing to build it for me please email me with a price quote of how much over the cost of the parts you would be willing to build it for. Schmidtzen (att) Gmail(dot) com