Remote controls have always been an intriguing device for all of us because of one good reason: It allows us to operate distant gadgets with a flick of a button, without having to move an inch.
Introduction
Today with the advancement of technology remote control switches have become accessible very easily from the market and we can buy such units quite cheaply and install them as per our own specific needs.
Today you can buy a remote control module from your local dealer or even more easily from an online store at very reasonable costs (for about $10).
These units will basically come with a receiver module neatly enclosed inside a small plastic box. The relays inside this receiver can be toggled using a small transmitter unit enclosed inside another tiny plastic enclosure accompanied with a key chain like attachment.
There are many versions of the above system, depending upon ones needs the particular type may be ordered.
The most basic one has a single relay which may be controlled through a single button over the given transmitter unit.
Common Technical Specifications
Other models come with 2 relays, 4 relays, 8 relays etc. which may individually controlled by pressing the relevant buttons over the associated transmitter key chain arrangement.
The transmitter is powered through a small button cell which might take to get exhausted while the receiver module needs to be powered through an external AC/DC 12V 100 mA power supply.
The relay outputs are very neatly terminated at the edge of the module using connectors. You just have to identify the respective pin outs and wire the electrical loads across these connectors as per your own specifications.
Where this Remote Control can be Used
The remote control can be very effectively used for remotely operating shutters, water pump motors, garage doors, apartment gates and doors, it can be also used in cars and vehicles for locking doors and ignition systems.
You may also find these gadgets useful for controlling household electrical items like lights, fans, ACs, and other similar gadgets just by a press of the respective buttons.
The Code Hopping Feature
Another cool feature with these advanced remote control systems is the code hopping feature which makes the signals generated from the transmitter absolutely fool proof.
The codes are automatically changed and made compatible with the transmitter and receiver making it impossible for the hackers and other malicious agents from copying your secret remote transmissions.
Ans whats more, in case your transmitter handset is lost, the system also incorporates a "code learning" operation, which enables you to interface any different remote with your existing receiver by pressing a single push button situated inside the receiver module....once the receiver and the new transmitter "shake hands", you can use them together very safely as these both units now become "made for each other".
Dan Mellen says
Hello Swagatam,
I am interested in building a remote release for my trap shooting club. I tried to use a garage door opener to release the clays but it was too slow. there was a delay between pushing the button and the release of the clay. I need a very fast signal, can you suggest anyting here?
Swagatam says
Hello Dan, I think the selected solenoid machine is not strong enough, you must try a stronger solenoid which would be able to "shoot" at a greater speed and force
Leonel Barradas says
Hi Swagatam,
I hope you're still responding questions regarding this thread. I'm currently trying to work in a project with the following requirements
I need a master RF remote control with one single channel and I want to simultaneously turn on 4 LED lamps distributed through my room. This means that every lamp should be in sync with the master Tx.
I was thinking to buy 3 sets of these Tx and Rx that you describe in this article and then pick one transmitter as the master and sync up the 3 receivers with that transmitter with the "code learning" function…
Kindly provide your thoughts as to what would be the best approach for my project.
Thank you
Leo Barradas
Swagatam says
Hi Leonel.
yes I think that's possible, you simply have to sync up the Rx with the Tx using "code learning" feature and then you can toggle each Rx with the same remote, by pressing the relevant buttons and switching the corresponding relays.
DILIP GHOSH says
Dear Mr. Majumdar,
Is it possible to control the speed of the fan with this circuit? If, so please show the process,also show the 240 V input/out.
Regards,
Swagatam says
Dear Mr. Ghosh, it might cost you around Rs.800/- doesn't look worthwhile to me.
but it's possible..and the procedures could be too lengthy….
Vineeth Gurudev says
Hi,this is vineeth gurudev !
I am a Btech first year student .I am very eagered and intrested in making remote based operators.my problem is that i don't know about the circuits of different types which are used in remote controlling and i don't know which circuit gives which type of out put.so can u please explain me in detail from basics as iam am a primary learner.
Swagatam says
Hi, a remote control device involves a lot of complex electronics, so you will have to first learn the basics of electronics and then think about learning remote controls….it could take many months and years for the course to finish.
Maya B says
Hi Swagatam and Raj,
Like Raj suggested, it would be great if someone can publish a circuit here on this blog. Also, I am curious if the single push button on the receiver can be modified for if and when type of operation (that is without physical "PRESS" of this button) such as video record or alert insiders when intruder passes certain perimeter of your house or turn the lights on at dusk, or turn on coffee maker when you step in the shower in the morning so that coffee will be ready when you get out of shower, etc. That would be greatly helpful for automation.
Swagatam says
Thanks Maya!
It will require some thinking…I'll try to post it, hopefully soon.
Raj Mukherji says
Hi Swagatam,
Why don't you publish something like the wireless doorbell just like the cheaply available Chinese remote control doorbells?
It will then be fun and thrill to work on such a low power UHF project at home.
Regards,
Raj
Swagatam says
Hi Raj,
I had opened one remote door bell circuit to learn the details, though everything was absolutely understandable, except one small part which I assume was a crystal, couldn't be identified properly. I replaced it with different value crystals for both the sets but they just failed to respond. I am sure whether its a crystal or something else, because from the appearance it looked like a small cylindrical can with two leads as we find in small quartz watches.
If I can break that part's identity then probably a very simple yet highly accurate remote control circuit will be at my disposal. If I can do it someday in the near future will surely post the details here.
Regards.
Raj Mukherji says
Hi there,
In fact I also did exactly the same thing. I could design the Transmitter successfully. However, I am stuck with the Receiver. I will share with you my working Tx circuit soon.
As far as your situation is concerned, if you are referring to the "unidentified" part as a crystal then please check the transmitter, if the connection is as follows:
Assuming it to be a crystal: One end of it should be directly connected to the Base of transistor S9014 while the other leg is connected to a 2.2nF capacitor which in turn is connected to the Collector of another S9014 transistor. If this matches your Tx circuit then you can safely use a 32KHz crystal for both Tx and Rx.
I have found that the Tx is using a Colpitts and a Crystal Oscillator. You may also find a small variable brass core inductor on the Tx to tune the frequency of the Tx with the Rx.
Now, my issue lies with the Rx part. It uses a Tank circuit comprising of 1.75 turns of enameled copper wire with a 4 pF capacitor in parallel. One end of the tank is connected to the positive supply via a resistance while the other end of the tank circuit gets directly connected to the Collector of S9018 transistor with a 8 pF capacitor between the Emitter & Collector which I guess to be the feedback capacitor.
I am getting stuck with the following areas:
a. I don't know the SWG if the enameled copper wire. Tried with a 24 SWG wire but did not work
b. I don't get 4pF and 8pF capacitors in the market. 4.7pF and 8.2 pF are available but will they work correctly? I can even add 3.3 and 4.7pF in parallel to make an 8pF but can't match anything suitable for a 4pF. So, your views on this can also help a lot in building my Rx unit.
Waiting for your comments and feedback.
Regards.
Swagatam says
Hi Raj,
If you could crack the crystal values for both Rx and the Tx, then the rest should be easy to follow.
Capacitors shouldn't be critical, a 4.7 will definitely work in place of a 4pF, because the variable inductor gives us plenty of space and option of adjusting the transmitting frequency as per the particular specs.
Even the wire SWG is not highly critical, you can match them by visual checking, for accurate confirmation you may use a vernier calipers but that may not be strictly required.
Thanks and Regards.
Raj Mukherji says
Hi,
Thanks for replying back.
I could not get a variable inductor in the market here in Kolkata. I also could not figure out the inductance of such an inductor. Can you suggest something on this (value/model no etc)?
Besides this, in the RECEIVER circuit, I used two 8.1pF in series across Emitter-Collector of the oscillator transistor to make 4.1pF while I used an 8.2pF across the 2.75 turns inductor to form the tank circuit. However, this is not getting synchronised with the frequency of the transmitter. Therefore, I want to use a trimmer to match the frequency of the Rx with that of the Tx.
Can you please advise, if I should connect the trimmer across the inductor of the tank circuit or across the Emitter-Collector of the oscillator transistor?
Waiting for you suggestion.
Regards.
Swagatam says
Hi Raj,
OK, then you can use a common 33pf type trimmer and connect it in parallel to the inductor. Before doing this you will have to remove all the capacitors that's connected parallel to the coil. The trimmer becomes the only capacitor now across the coil.
In this way you would be able to tune the LC tank to any desired frequency that would hopefully latch on with the complementing set or the circuit.
Regards.