Ht12e/d input output logic question

Thread Starter

Archaeus

Joined Sep 10, 2016
34
Good day. I'm currently in the soldering phase of an RF circuit designed to operate an l293d motor chip. On the breadboard I managed to get it to work, but after soldering (and checking for shorts) I am not getting proper high/low signals sent through the encoder/decoder from 2 2p2t switches to the motor driver chip. The only variable I can think of is that in soldering, I put the positive leads from the switches to the 9v rail instead of the 5v regulator chip like I did on the breadboard. The data sheet says this is still within operating range for the encoder. Would a difference in voltage sent to the encoder data pins effect the transmitter signal to the decoder and out to the motor chip? As far as I know, they just operate on logic high/low signal. Thanks for any help.

There are a few errors in his designs, but it' configured like this
http://www.instructables.com/id/homemade-rc-car/
 

Thread Starter

Archaeus

Joined Sep 10, 2016
34
I changed the switches from his design to output from the commons with alternating positive/negative in the closed positions for reversable polarity. Rest of schematics are identical.
 

AlbertHall

Joined Jun 4, 2014
12,345
I put the positive leads from the switches to the 9v rail instead of the 5v regulator chip like I did on the breadboard. The data sheet says this is still within operating range for the encoder.
Is the encoder supply pin also at 9V or is it still fed from 5V?
If the pins have been connected to 9V but the chip VDD is at 5V this is not good and may damage the chip.
 

Thread Starter

Archaeus

Joined Sep 10, 2016
34
Is the encoder supply pin also at 9V or is it still fed from 5V?
If the pins have been connected to 9V but the chip VDD is at 5V this is not good and may damage the chip.
Yeah I just read that on the data sheet... Allowing is vdd+0.3v. The chip is 5v regulated. I didnt run the switches for very long, but I know it doesn't take much. Might have fried the protective diodes. Any ideas to test it other than taking voltage readings at the motor chip inputs to see if high/low is alternating? Thanks for the reply.
 

AlbertHall

Joined Jun 4, 2014
12,345
Connect the pins to the correct voltage and see what happens at the output pin of the encoder. If you measure the voltage there then it should rise from zero to something like 2.5V.
 
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