encoder / decoder issues HT12E & HT12D

[MrDEB]

using this schematic http://multyremotes.com/four-channel-ASK-remote.htm BUT am only using two data inputs instead of 4.
The circuit works but I only used a 4 pos dip switch(D0-D3) and one push button. No diodes.
Upon pressing the push button I get the receiver to respond using LEDs on all 4 outputs. The LEDs work as planed BUT they stay on too long.
Studying the schematic for the transmitter, it has 8 1n4009 diodes, D1-D4 on the data inputs and D5-D8 on the Te pin.
I get the reasoning behind the D5-D8 diodes (to isolate the TE pin from any other button presses but D1-D4 is open for discussion as to WHY?
This might by why the LEDs stay on too long on the HT12D. This is where I am headed but using 1n4148 as I have no 1n4009 ultra high speed switching diodes.
This might save someone the same issues??

[brad]

Hmm, it could be to prevent the I/O pins having effecting the TE pin? I.E. If there just happened to be a logic 0 on one of the pins it would be the same as pushing one of the push buttons - the diodes will prevent this from ever happening.

Other than only using two inputs, have you built the circuit just like the schematic?

[MrDEB]

Only using two data pins. My circuit is exactly as the schematic except I left out the diodes going to the data input(the diodes on the TE pin are in place)
I came up with a solution to reset the decoder(receiver end) by toggling the Vdd using a port pin on the 18F2420. The HT12D only draws 8-10ma max. It works but not really a good practice in my estimation. I contacted the company to see if they have a different solution. Other than that these encoder / decoder chips work great. I am thinking that with the 255 address combinations and 15 data input combos a-lot could be done with these chips.

[brad]

I'd just follow the schematic as is and all should be good for you

[MrDEB]

The data sheet states that the HT12D latches remain latched with the last data and won't change until a new data stream is received. Tried configuring an RC circuit that would take the TE low to transmit a new data stream as a "clear data latches" but no success.
Toggling the Vdd works quit well

[brad]

Did you try the circuit as per the schematic?

[MrDEB]

YES exactly as per schematic.
Did some research and find that in the data sheet it states that the data latches remain as per last data stream UNIT a new data stream is used. TRied several things but nada.
Configuring a method to send out a different data stream that switch positions is where I am at.
While in bed last night I realized I need a piezo or ? to beep when the turn signal is signaling left or right. Thinking maybe using a 7555 to accomplish this and reset the data stream (TE low). Wonder if them 3909 chips are still around in SMD or ??
The pcboard for the transmitter at present is 30mm x 40mm. not much room for much else.?

[brad]

Were you looking to use the 7555 as an oscillator to drive the piezo?

[MrDEB]

YES but one small problem. I need two 7555 since a 7556 is no where to be found
senerio= when a switch goes LOW it transmits a data stream that tells the PIC to signal LEFT. When the TE goes LOW via the tilt switch it triggers a monostable timer for say 5 seconds HIGH which triggers an astable for a few seconds of pulses until the monostable times out(output goes LOW) the astable output goes LOW.
.
Was wanting to connect to the TE pin of the HT12D but it keeps the data stream the same so no help in reseting the HT12D latches(using A3 to power the HT12D, just toggle the pin to reset.

[brad]

How about just using a cheap microcontroller to take care of it for you? perhaps an 18f25k20?

[MrDEB]

That's exactly where I am now. Drew up a schematic yesterday using an 18F1220 but will look at the 18F25K20.
Using a pIC in the transmitter will solve several issues.
A way to reset the receiver latches instead of toggling the Vcc pin on the HT12D
cure ANY or most any switch bounce as the tilt switches will be bouncing most of the time.
Can output two different signaling sounds for left or right.
The switch bounce is what my big concern was/is.
Now to wire up a perf-board and try it out. Hopefully the switches will be here today.

[brad]

Sounds like a plan!