How to use Holtek 12E/D .............??

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
Hi,

Yesterday, i was reading data sheet of HT 12E/D, i am confused how to use add. pin & data.

In Encoder 1Mohm resistance is used & in decoder 51Kohms is used @ osc. pin.

please let me know how to connect IR led & photo diode with respect to Vcc or GND. ??
 

bhageria

Joined Jun 3, 2011
2
the address which you set in the encoder should also be set in the decoder..
for example:- if you set 00000001 in the encoder, then the address of the decoder should also be 00000001.
whenever you send a data, the decoder first checks the address..it checks the address three times and if the address matches then the decoder continues to decode the data.

Thus you can have 2^8(2 to power 8)= 256 combinations of address which again means that with a single encoder you can control 256 decoders just by changing the address in the encoder chip.

and sorry i got no idea how to connect IR LED and photodiode..
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
I am confused there is add. & data pin how to use??
in above i think you are talking of add. pins.

It will be nice if you post small fig. of it how to use it for basic.
 

hgmjr

Joined Jan 28, 2005
9,029
You mention the value of resistors. Can you post or provide a link to the schematic to which you are referring?

These devices are fairly straightfoward to use. As you may already recognize, the HT12E/D are a matched pair of devices. The encoder device transmits a serial bit stream that contains an address the value of which is determined by the address line that is active. The decoder is wired so that it is set to recognize the same address. With each message received by the detector, it checks the address in the message and then activates its data line if the address value in the message equals to the address it is wired to recognize.

They need to both be programmed to the same oscillating frequency in order to operate correctly.

hgmjr
 
Last edited:

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
Hi again,

the supply voltage is 5V(7805)

In ht 12E the osc pin are connected with 1Mohm resistance, the add. are left open and transmit enable is active low.

In decoder the osc resistance is 51Kohm, valid transmission is active high, add are left open & led are connect (without resistance) to data pins.

the main problem is that i am not getting how to connect IR led & photo Diode??
 

hgmjr

Joined Jan 28, 2005
9,029
In looking at the datasheets for the two devices, I see now what you were referring to as far as the resistor values are concerned. It turns out that the resistor value in the HT12E needed to set a given internal oscillator frequency is not the same as the resistor value needed to set that same frequency in the HT12D. You will need to select the design frequency that you intend to use and then refer to the graph in each of the two datasheets to determine what resistor value you need to use in each of the two devices to get them to oscillate at the frqeuency you have chosen. These two resistors will be different values. You may want to set up one of the HT12 devices with a resistor and a potentiometer in series so that you can tune the frequency in one to closely match the frequency in the other. That will give you the best performance.

hgmjr
 

hgmjr

Joined Jan 28, 2005
9,029
Transmit side
Receiver side

The two links above show the hookups for a transmitter and receiver circuit. The two 3-pin headers are where you connect the IR emitter in the transmitter case and the IR detector in the receiver case.

You wire the address lines in both cases to be the same.

Then when you press one of the buttons on the transmitter side the corresponding data line on the receiver will be activated.

hgmjr
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
IN above circuit you use an RF TX & Rx, but i want to connect IR led with photo diode.

& in the receiver side why transistor is connected??
 

hgmjr

Joined Jan 28, 2005
9,029
The two circuits shown are actually equally suited to IR or RF as the means of transmitting and receiving data wirelessly. IR transmission is by its nature limited in its distance and must be carefully mechanically aligned to insure the optimum transmission.

hgmjr
 
Top