Radio Frequency decode and decoderr for 27MHZ remote control

[zeller]

HI,

I have designed an AM receiver and transmitter.I need a chip or something else to encode and decode signals. 4 channels would suffice.Can anyone recommend the right chip.I am looking for something simple.


My receiver and transmitter use Amplitude Modulation.

Many thanks in advance.

 

[mister_rf]

You may use for example HT12A/E, HT12D/F series

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[albbg]

Please have a look to:

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[zeller]

Please have a look to:

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Thanks you all very much for the reply. I want to use HT12E as the encoder and HT12F as the decoder. How do I know that the HT12E would be able to communicate with HT12F ? if they will recognise each other? I am planning to buy these from the same supplier.

Thanks.

 

[mister_rf]

Yes
HT12E encoder and HT12Fdecoder = a pair of encoder/decoder

The 2¹² decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holteks 2¹² series of encoders (refer to the encoder/decoder cross reference table). For proper operation, a pair of encoder/decoder with the same number of addresses and data format should be chosen.

See details in the datasheet:

 

[zeller]

Thanks Misterrf for the help. Before this project I tried to use 600D and 600E ( works similar to HT12E) and I fear i may face the same problem with HT12E/D. The problem is when I connected the 600E and 600D all the LEDS on the decoder lit up even before any signal was received!! What was the problem? I double checked and everything was okay! I was expecting one LED to light up only when the appropriate switch on the encoder was pressed, but all LEDs did light up before pressing a single switch on the encoder.

I fear I may face the same problem on HT12E/D.

Please help me.
Thanks.

 

[zeller]

Please help me.

 

[mister_rf]

Usually there are no problems using the HT12E/ HT12D series circuits if you follow its datasheet guidelines. Keep in mind for the output data pins, power-on state is low.

 

[zeller]

Usually there are no problems using the HT12E/ HT12D series circuits if you follow its datasheet guidelines. Keep in mind for the output data pins, power-on state is low.

Sorry, it does not work.

The HT12E i am using 6v regulated dc.I have connected VSS with negative but connected nothing for A0 to A7.For the ROSC resistor I have used 1M ohm resistor. A8 to A11 i connected 12v LEDs to negative.TE is connected to negative.And VDD to +6V as usual.

For the HT12D I am using 9v regulated dc.I have connected VSS to negative and nothing for A0 to A7.Nothing is connected to VT (port 17) .For Rosc resistor I have connected 35 ohms resistor.D10 to D13 I have put switches connected to negative(when on).VDD is connected to +9v regulated as usual. Now I have connected DIN of encoder directly to DIN of decoder (port 14) just to test if it works.But when I switch on one of the switches on the decoder none of the LED lightens up.I have checked everything all looks okay.

Please help, what is wrong?Many thanks.

 

[zeller]

O

Sorry, it does not work.

The HT12E i am using 6v regulated dc.I have connected VSS with negative but connected nothing for A0 to A7.For the ROSC resistor I have used 1M ohm resistor. A8 to A11 i connected 12v LEDs to negative.TE is connected to negative.And VDD to +6V as usual.

For the HT12D I am using 9v regulated dc.I have connected VSS to negative and nothing for A0 to A7.Nothing is connected to VT (port 17) .For Rosc resistor I have connected 35 ohms resistor.D10 to D13 I have put switches connected to negative(when on).VDD is connected to +9v regulated as usual. Now I have connected DIN of encoder directly to DIN of decoder (port 14) just to test if it works.But when I switch on one of the switches on the decoder none of the LED lightens up.I have checked everything all looks okay.

Please help, what is wrong?Many thanks.

Please help me!

 

[FvM]

For Rosc resistor I have connected 35 ohms resistor.

Should be around 30 kohm (35 k would work as well).

According to your post, you have connected LEDs to the encoder (sender) and switches to the decoder (receiver). What do you expect from this setup?

 

[zeller]

Should be around 30 kohm (35 k would work as well).

According to your post, you have connected LEDs to the encoder (sender) and switches to the decoder (receiver). What do you expect from this setup?

Sorry, the ROSC is 44kohms and I haven't put the led on the encoder, they are on the decoder. i think the decoder is faulty.

 

[zeller]

Sorry, the ROSC is 44kohms and I haven't put the led on the encoder, they are on the decoder. i think the decoder is faulty.

Okay I have now checkd everything and connected as required.

When I connect the encoder and do a direct connection from the encoder output pin to decoder input,

The decoder LEDs A8-A11 light up after about 15 seconds and stay the same way.Now i have also connected an led on the VT pin on the decoder, this blinks on and off. When I connect each switch AD8 to AD11 on the encoder one by one nothing happens on the decoder.The LEDs stay on and the VT pin stil flickers.Please tell me that HT12E/D as not a fraud!!!!!

 

[zeller]

Please help me

 

[tpetar]

There is RF and IR project with PIC16F630, PIC16F628 :

https://jap.hu/electronic/codec.html



Before testing over RF try connection with wire RX and TX.
Maybe problem exist at your RX TX modules. Can we see your modules if not military secret ?

 

[mister_rf]

So you are using a pair of HT12E/ HT12D.
For the 12HTD (decoder) the recommended f_OSCD oscillator frequency is 50*f_OSCE as in the HT12E ( encoder). In theory for the encoder at 6V and using a 1M resistor we obtain a 3KHz oscillator frequency, so decoder side we need to have 150KHz. Check the graph attached, 150KHz and 9V power supply-> the estimated resistor value = 68k-75k.
For the HT12E encoders, transmission is enabled by applying a low signal to the TE pin. If a transmission enable signal is applied, the HT12E encoder scans and transmits the status of the 8 bits of address(A0 – A7) and 4 bits of data (AD8-AD11) serially in the order A0 to AD11.
Pins 1...8 of encoder are for setting the unique signal and important to set the same pins of decoder with identical settings, otherwise the receiver will not decode the signal.
The HT12D is arranged to provide 8 address bits and 4 data bits and the VT pin goes high to indicate a valid transmission and can be used as a momentary data output.

 

[zeller]

So you are using a pair of HT12E/ HT12D.
For the 12HTD (decoder) the recommended f_OSCD oscillator frequency is 50*f_OSCE as in the HT12E ( encoder). In theory for the encoder at 6V and using a 1M resistor we obtain a 3KHz oscillator frequency, so decoder side we need to have 150KHz. Check the graph attached, 150KHz and 9V power supply-> the estimated resistor value = 68k-75k.
For the HT12E encoders, transmission is enabled by applying a low signal to the TE pin. If a transmission enable signal is applied, the HT12E encoder scans and transmits the status of the 8 bits of address(A0 – A7) and 4 bits of data (AD8-AD11) serially in the order A0 to AD11.
Pins 1...8 of encoder are for setting the unique signal and important to set the same pins of decoder with identical settings, otherwise the receiver will not decode the signal.
The HT12D is arranged to provide 8 address bits and 4 data bits and the VT pin goes high to indicate a valid transmission and can be used as a momentary data output.

Thanks Mr Rf that now works I have cheked by direct connection between ht12e/d. Now I am using a double balanced mixer (sa60N) to mix the 27 MHZ carrier signal with the signal from HT12E for rf modulation. This is AM Modulation.I have got a 200MHZ digital digital oscilloscope (DSO).Now I want to make sure that the two signals are mixed properly and I can 'see' AM modulation on the DSO. This may seem simple enough but how do I 'measure' amplitude modulation using the oscilloscope? Sorry for a simple question but I'm still a newbie in rf measurements.I can't see the AM 'pattern' on the normal measure of frequency on the oscilloscope.

Thanks.

 

[mister_rf]

Amplitude modulation can be measured using an oscilloscope. There are two simple methods of doing this: one measures the modulation envelope, and the other method uses a trapezoidal pattern for measurement. More details for example here:
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---------- Post added at 22:56 ---------- Previous post was at 22:51 ----------

Watch this video:

 

[FvM]

The usual AM method used with H12 and similar encoders is ASK (amplitude shift keying) also called (OOK) on-off keying. It's in fact easily to detect.

 

[zeller]

Amplitude modulation can be measured using an oscilloscope. There are two simple methods of doing this: one measures the modulation envelope, and the other method uses a trapezoidal pattern for measurement. More details for example here:
**broken link removed**

**broken link removed**

---------- Post added at 22:56 ---------- Previous post was at 22:51 ----------

Watch this video:

Okay Thanks.But I have checked my oscilloscope and did not find any measurement for 'trapezoidal pattern' does it come under a different name?.Is this a standard measurement on every scope?All I want to do is see the effect of the Ht12e on the amplitude of the carrier wave.