Problem with wireless serial transmisson

[gaurav_sharma132]

As I have bought two ask modules (tx and rx) operated at 434 MHz..
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ThinkLABS roboSHOP - India's Online shop for cost effective and quality robotics kits, components, microcontroller development board, motors, sensors, robot kit

And I want to make remote control robot for that i am using two AT89C51 and using serial transmission. The motors are running properly when I attach TXD and RXD through wire simply. But when I introduced this module the circuit is not at all responding I felt that if there is no connection b/w two 89C51 they are operating on their own. As i am checking the circuit on breadboard first...


So please help me out......unable to achieve wireless transmission

Regards
Gaurav Sharma

 

[Nigel Goodwin]

You really need to use some kind of coding, such as Manchester coding, you can't just stick RS232 in and out with standard modules.

 

[gaurav_sharma132]

No, I am not using RS232 i am using serial pin of AT89C51....

Basic, Block Diagram is

transmitter (AT89C51) pin 11 i.e TXD --->> 434MHz ASK Transmitter Module

--->>wireless medium--->434MHz ASK Receiver Module--->> Receiver

(AT89C51) pin 10 i.e RXD--->> L293D Driver--->> control motors


we have similar working circuit at ThinkLABS roboSHOP - India's Online shop for cost effective and quality robotics kits, components, microcontroller development board, motors, sensors, robot kit


Regards
Gaurav Sharma

 

[Nigel Goodwin]

No, I am not using RS232 i am using serial pin of AT89C51....

The serial pin provides output suitable for RS232, it the same signal, just needs converting (and inverting) to RS232 levels by a MAX232 or similar.

You might try putting a hardware inverter between the modules and the processors, this may give you some results, but you really need Manchester coding, and not to use the hardware UART's.

 

[gaurav_sharma132]

As I am firstly making the circuit on breadboard....

It is not a standard RS232 connector.... TXD pin simply transmit the data serially for ex. 1010
and RXD pin on other side receive that data serially as 1010 which is transmitted
and it is TTL logic and there is not any use of any voltage level converters like max232.....



Regards
Gaurav Sharma

 

[Nigel Goodwin]

As I am firstly making the circuit on breadboard....

It is not a standard RS232 connector.... TXD pin simply transmit the data serially for ex. 1010
and RXD pin on other side receive that data serially as 1010 which is transmitted
and it is TTL logic and there is not any use of any voltage level converters like max232.....

No, you don't need them, but the signal format is the same - and won't go through a wireless module.

Although it's for PIC, check my wireless tutorial which explains further.

 

[gaurav_sharma132]

I am not using PIC. I am using AT89C51 as already told......And i am making remote control robot not PC controlled robot.

Tell me then how can I proceed ......


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Regards
Gaurav Sharma

 

[mvs sarma]

I am not using PIC. I am using AT89C51 as already told......And i am making remote control robot not PC controlled robot.

Tell me then how can I proceed ......


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Regards
Gaurav Sharma

whether the 89C51 is bought with software loaded or you have locally programmed? generally 89C51 can be programmed only using HV programmer and not ISP programmer. if you were trying to use ISP type, you need to change to 89S51(2).

 

[gaurav_sharma132]

I have programmed it..both transmitter and receiver IC's.

And I am also having Atmel 89 series programmer used for burning the program.
It supports almost all types of Atmel 8051 type mcu....so it supports AT89C51 too.



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Regards
Gaurav Sharma

 

[Nigel Goodwin]

I am not using PIC. I am using AT89C51 as already told......And i am making remote control robot not PC controlled robot.

Tell me then how can I proceed ......

Yes, I know you're not using a PIC, but my tutorial will help you understand your problem - and save me typing it all here.

PIC Tutorial Twelve - RF Remote Control

 

[gaurav_sharma132]

ok let me read then I came back to u again.....

 

[gaurav_sharma132]

No, I didn't get exactly.........Please help me out.

I think that it should work like in the way I am doing......

But totally exhausted...........




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Regards
Gaurav Sharma

 

[Nigel Goodwin]

No, I didn't get exactly.........Please help me out.

I think that it should work like in the way I am doing......

As I've already told you, it won't - a wireless link is AC coupled, not DC coupled.

Your easiest option is to try a hardware inverter at either end, a simple transistor and two resistors is all you need - this may make it work reasonably.

I presume you are using a decently slow baud rate?.

 

[Triode]

I actually got a device just like this one, with a single on/off channel running at something like 433 mhz. It was on a really good sale so I threw it in when I bought my junebug, have to pay shipping either way. I haven't messed with it yet, but I was thinking baud rate would be a concern. My first guess would be that with a 433hz transmitter/reciever you might be limited to half that for the baud rate. But again, thats just my first guess, I havent gotten into it yet.

 

[gaurav_sharma132]

As I've already told you, it won't - a wireless link is AC coupled, not DC coupled.

Your easiest option is to try a hardware inverter at either end, a simple transistor and two resistors is all you need - this may make it work reasonably.

I presume you are using a decently slow baud rate?.

firstly, why do i need data inverter...??

Secondly,I am using 9600 baud rate then I found that it is too fast then I switch to 1200 bps it is still not working....


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Regards
Gaurav Sharma

 

[Nigel Goodwin]

firstly, why do i need data inverter...??

READ MY TUTORIAL THAT EXPLAINS WHY!!!

Secondly,I am using 9600 baud rate then I found that it is too fast then I switch to 1200 bps it is still not working....

Depending on the modules they may not work at 9600, but 1200 or 2400 should be fine - but (AGAIN!) they won't work like that - my tutorial explains why.

 

[gaurav_sharma132]

In RF remote control tutorial ???

 

[Nigel Goodwin]

In RF remote control tutorial ???

Obviously, where else would it be?.

 

[colin mac]

What do you want to do? If you just want to send a few commands to a robot, then
you can use the HT12E and HT12D with your modules. That way you only need to deal with parallel data.

 

[gaurav_sharma132]

What do you want to do? If you just want to send a few commands to a robot, then
you can use the HT12E and HT12D with your modules. That way you only need to deal with parallel data.

But actually I want to control Two DC motors and also want to control the speed of DC motor that I think can be done with the help of micro controller only.

But I not understand that RF modules work fine with HT12E and HT12D. Then what is problem with AT89C51??

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Regards
Gaurav Sharma