• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

RF circuit with HT12E and HT12D

Status
Not open for further replies.

krishmidhun

New Member
Hi, I have made a simple RF circuit with HT12E and HT12D. My problem is that when I press any switch on the transmitter and cut power to the transmitter by holding push switch, the receiver end is still showing a LED output. I want it to go to the default state of all LEDs off whenever transmitter goes out of range or power to it is cut. Please help me on this.
 

Attachments

RadioRon

Well-Known Member
The HT-12D has a latched output so the circuit is, unfortunately, functioning as designed. To change the function to match your goal, perhaps we can add some additional circuitry to the transmit side. For example, it would be possible to add a power on/off circuit to the transmitter so that when the power is switched off, the transmitter sends one last message but with the data word forced to be "1111". In order to do this, we would need to add a local power storage filter (for example a series diode following by a larger value capacitor), plus a circuit to sense when power has been removed from the tx which signals the data bits to become all ones, and a gate or transistor at each data input controlled by this sensing circuit.
 

krishmidhun

New Member
The HT-12D has a latched output so the circuit is, unfortunately, functioning as designed. To change the function to match your goal, perhaps we can add some additional circuitry to the transmit side. For example, it would be possible to add a power on/off circuit to the transmitter so that when the power is switched off, the transmitter sends one last message but with the data word forced to be "1111". In order to do this, we would need to add a local power storage filter (for example a series diode following by a larger value capacitor), plus a circuit to sense when power has been removed from the tx which signals the data bits to become all ones, and a gate or transistor at each data input controlled by this sensing circuit.
can't we do any changes in receiver end? instead of transmitter side. because the transmitter should be small in size, hence i can't add anything to it.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I have tried using VT as output. but the problem is the output from the VT is flickering some times. Is there any solution to get stable the output from VT
VT signifies a valid signal received, so any errors means it will drop out - but what EXACTLY are you wanting to do?, and why are you using IC's unsuited for your purpose?.

We get endless questions about these devices here, and always because people are trying to use them for the wrong purpose.
 

RadioRon

Well-Known Member
The changes to the transmitter would be very modest. I suggest the circuit in the attached figure as a starting point, although I admit it is a bit crude. In that circuit, D1 and C insure that power continues to be supplied to the encoder and transmitter for a short time after 5V is removed. However, in that time, Q1 - Q4 are turned off, so the code that is sent is "1111" for that short time.ht-12b006g.gif
 

krishmidhun

New Member
VT signifies a valid signal received, so any errors means it will drop out - but what EXACTLY are you wanting to do?, and why are you using IC's unsuited for your purpose?.

We get endless questions about these devices here, and always because people are trying to use them for the wrong purpose.
What i am planning to make is a "passive keyless start" for my bike. There will be a RF receiver which i have made using HT12d and a RF remote with HT12e. When the remote present in the range of receiver, a relay connected to receiver should latch and dislatch when remote will go out of the range.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top