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remote control using radio freq

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Our project has been approved and now we need to build our prototype.

As I research, our project is basically a radio controlled device. Push a button in the transmitter side and when it was received by the receiver it buzz or light.

I know it is quite simple compared to examples shown in sites. ???

Now I don't know how and where to get started. I'm thinking of using pulse modulation to send commands. Command to light or sound.

Thanks in advance ;)

Note: I'm fairly new in practical electronics. As I have already studied
theories.. I think I can learn well.

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to MP
wow! that's one hell of an amazing device!! honestly, if I look and examine its every detail, its perfect for my project. With its security and features.. wow.. but the 433Mhz chip cost around $54 uhh.. but a whola thanks!!

to trigger
this is what I have tentatively decided:
minimum of 10m
around 2.45Ghz *same as bluetooth
PM (Pulse Modulation)
uhh.. i still don't have an idea

thanks! ill update to find more circuits :)

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2.4GHz ISM band is a bit difficult for me esp. to build transmitter, because it involves a lot of matching problem.
Although you can build using simple LC+transistor circuit but if you don't have a spectrum analyzer or signal generator, it will not an easy job.

For me, I will start with 433.92MHz where it is simple and need lesser equipments esp. you can build a transmitter using saw resonator and a transistor based receiver.

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higher frequency will have more interference esp. 2.4GHz band......
like microwave oven, DECT phone, wireless lan, Bluetooth etc.

For 433MHz, I think if you are in UK, the most problem will be caused by the TETRA (police RF communication ?? not sure, it is at 426MHz). You have to build a narrow band receiver to prevent jamming from it.

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You need to find a better place to shop for parts. You can get this whole kit for $40 or just the module for $13. This is a kit from electronickits.com
The exact link for these parts or the kit is here:

Hope it helps you along on your project.


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hello I'm back! :)

btw, before I continue on.. I would like to give a lotta of thanks for trigger and MP for helping me on this project.. thanks a lot!!

Something strikes me while listening to my instructor bout 555 timer. And this what I think how my circuit should be (below)

and now i think there's a problem.. the two signals might not synchronize each other.. one might be low and one might be high.. i have to ditched the comparator i think..

my goal is to use PWM(pulse width modulation).. so i think the receiver would check the width of the pulse rather than compare it with the (same pulse width)--needs synchronization.. if there's only a way to measure the width of the pulse..

thanks in advance.. actually i'm happy if I could build the circuit by myself.. :)


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thanks trigger! :)

i have researched on the tone detector IC LM567 and found it.. uhh.. confusing ???

well, i have decided to take a look at my electronics book if I could find anything that would help my project. Phased-Locked Loop interest me. After reading all the explanation in the book plus a tutorial on the net, I found that this what I'm looking for, the PLL!!

Phase-Locked Loop (PLL) is an IC that synchronize two signals and output a voltage proportional to the phase and frequency of the input and self-generated frequency.

PLL IC's come in form of NE566, LM566, NE565 and LM565... I just noticed a similarities... LM567 is also a PLL! hehe.. sorry I'm so dumb to realize it sooner. Thanks again trigger!

I'll be back to post a circuit of my design. :)

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  • 3 weeks later...


so far this is the flow of my circuit:
555 timer(information,encoder) -> fm transmitter(carrier, modulator) ~~~
~~~ fm receiver(demodulator) -> PLL (decoder) -> output

i'm now in the process of testing transmitters and receivers..
i' ve come across this very nice fm transmitter: http://tacashi.tripod.com/elctrncs/smplfmtr/smplfmtr.htm

i'm planning to supply my transmitter and its receiver at 3 volts.

is there any 3v fm receiver that is simple enough for my project? Thanks!!!

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yeah.. hopefully we can make a fully working prototype by next week..

I checked TDA7000 and TDA7088 IC's and looks like they're a complete fm receiver with no amp..

and I assume MC3361 and MC3362 is the amp right?

I wanted to run my receiver with 1.5V battery to reduce weight and I think these components would serve my needs..

As always, many thanks to trigger for your continuous support and help for my design project. May god bless you on your way :)


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I think I am wrong......
because those ICs I mentioned isn't operate in 1.5V......

And I think it is quite difficult to source for radio IC which operates in 1.5V for howbrew......

I am playing now with Toshiba TA2104 but its minimum voltage is 1.8V........ :-[

And MC3361 and MC3362 are not amp, they are IF front end where they are widely use for wireless intercom circuit for many years...

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Did you check for a DC-DC converter inside that wireless MIC ? most circuits that run off a single cell use a small DC-DC converter to up the voltage to a more reasonable 3.3v or 5v.

Maxim IC makes some really simple dc-dc converter chips, with only a few external components needed. Ive used the MAX1674 before.

If you want to have a working prototype in a week or two, you should probably find a finished design instead of starting from scratch..

A 555 timer is good for about 1mhz max, depending on which model, I think most of them only go to 500khz..

Prebuilt transmitter/reciever modules are really a bargain.. and let you spend more time on the rest of the circuit.


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thanks Chester for some thought :)

yeah.. maybe there's some step-up ic inside .. coz the device also light a red LED to indicate if there's a signal (i know LED doesn't work on 1.5v).

it's around 10 days before our defense and i hope we can get the circuits fully working as soonest possible time.

wish us luck.. thanks everyone! :)

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  • 1 month later...


I wanted to take this time to thank everyone for sharing their time and knowledge to make this project possible. At last, we passed our design project. The only downside is that we had used infrared instead of radio frequency to give us more time to focus on the encoding and decoding section of the project.

Now that I have more time available, I'm planning to continue our original project. The time we spent on building the project had given me lots of knowledge on the electronics world.. heheh.. I really mean, I really learned a lot!

By the way, if you're interested here is the schematic for the transmitter and receiver section. Note that it uses infrared as a wireless links :(


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