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HT12D and HT12E issues

I have an addressing issue with these chips. The only address that works between encoder and decoder (that makes VT go high) is leaving all 8 address pins floating. Tried all low with dip switch, no go. The datasheet looks like it should work as long as dec and enc have same address. Do any of you use pullups on the address pins?

Thanks.
 

shingabiss

New Member
My question was specifically about the HT12D and HT1E 8 address pins and how they are not behaving as per datasheets. The HT12D's VT signal only goes high (indicating enc and dec addresses match) when the addresses on both chips are floating. Tying any low, even when they both match will not drive VT high. I am wondering if others have encountered this.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Do you have the oscillator frequencies set correctly? The decoder should run at 50x the encoder frequency.

A wrong frequency could possibly cause problems such as address confusion, due to the data being misinterpreted?
 

shingabiss

New Member
5VDC.

I think the chips I have are poor quality knock offs that don't really function well. I've ordered some real Holtek chips and will give them a try.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
On the data sheets I have, 1.1M would give about 2.75 KHz at 5V, while 51K on the decoder is spot on for 3KHz encode.

It may be worth reducing the 1.1M to 1M ? I have no idea how critical or otherwise the frequencies are...

Or it could well be the devices, if they are fakes.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Exactly what are you trying to do with the chips? - generally all the problems on here with them are when people are trying to use them for other than their intended purpose. They are designed as 'TV' type remote control chips, with a keypad on the transmitter, and the outputs of the receiver feeding various relays etc.

But often people seem to think they are general purpose communication chips from micro to micro.
 

shingabiss

New Member
Simply to communicate between two Arduino Unos but that's really irrelevent, I am breadboarding them now trying to run them through a basic functionality check.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Simply to communicate between two Arduino Unos but that's really irrelevent, I am breadboarding them now trying to run them through a basic functionality check.
It's not irrelevant - that's not what they do - and that's why all the threads here about having problems with them are people wanting to do that.

It's a simple TV style remote, and that's it.
 

Pommie

Well-Known Member
Most Helpful Member
Why don't you just use spi or I²C, there's lots of examples available - they're actually intended for communication.

Mike.
 

shingabiss

New Member
This is a 433mhz wireless connection where the 'communication. consists of the 4 data bits on the HT12D/E. It only has to turn a few things on and off. I like the 433mhz/encoder/decoder setup for this because it is stand alone, no protocols needed and quite adequate for the task.

I guess it seemed like a weird use of these but I like it, if only the chips would behave as the datasheets state. I've bradboarded exactly what is shown in the diagrams. I've been doing this kind work in R&D for over 30 years and never felt stupider or more dumnbfounded in not getting this to work. The assressing only maches up when all are left floating, datasheet says as long as they match. The other issue is the receiver 4 bits don't change state when xmt bits are changed, makes no sense. I breadboarded it a few months ago and it worked as should. I just went and got a new batch of chips thinking I might have some defective ones. Using the same bench supply as before. Honestly my lab feels like the Twilight Zone with these ICs lol.
 

Pommie

Well-Known Member
Most Helpful Member
First you say you're communicating between two Arduinos then you say you're not.

Mike.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Have it your way.
It's not me who's struggling :D

Like I said, historically almost all problems with those chips here have been people, like you, misusing them.

Apparently it 'can' be done, but it seems very difficult to manage to do so.

If you haven't got official chips?, then that probably isn't going to help - there's an incredible amount of fake components coming out of China.

I'm presuming you're also using cheap Chinese radio modules?, they often don't seem very clever either - have a look at this video about testing the HT's:

 

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