NZFF

I have read on another site where a rotary quadrature encoder (e.g. ALPS EC11B) has been used with a quadrature clock convertor (LS7183) and an analogue switch (MM74HC4316N) to simulate repeated pressing of a keyboard button when the encoder is rotated. See post 6 here; http://www.mp3car.com/vbulletin/hardware-d...re-decoder.html

I have the output of the analogue switch connected to the pins on the keyboard matrix.

If I connect LED's thru the analogue switch I can get LED's to flash (albeit very dimly) when I rotate the encoder, but I cannot get the analogue switch to simulate the key press. Other push buttons that I have connected to the matrix work OK. These buttons have a resistance of about 70 ohms, the analogue switch appears to have a closed circuit resistance of about 100 ohms.

I am using an MC14066B instead of the MM74HC316N. Is the resistance across the MC14066B too high compared to the MM74HC316N?

I think part of the problem is the very narrow output pulse width from the LS7183 (which from the datasheet can adjusted up to 140 microseconds long). I also wonder what the resistance is across the switch actually is considering the narrow output pulse from the 7183.

Has anyone used these items in this manner?

Can anyone provide some ideas to make this work?

Thanks.

I think you are right - the 140 microsecond pulse is not going to be long enough to be picked up by the multiplexed keyboard scan sequence. You could feed the pulse into a 555 monostable circuit to extend the pulse length? Cheers, Wayne.

Using a 555 is certainly worth a try.

I got the impression that this had been done without using any other components other than the encoder, conveter and the analogue switch. I wondered if I was getting something wrong somewhere. I started off using a DIL relay. I could hear the relay trying to operate but it wasn't pulling up enough to close the contacts, that's when I went to the MC 14066B.

I do agree though that extending the pulse length is going to help the situation and should fix the problem. I've used 555's before but didn't think of them this time.

Thanks for the tip.

What the heck are you guys talking about??

All you need to know is that a 555 timer can solve most of life's problems...

Hi Wayne,

Thanks for the tip on the 555. Got it to work nicely, needed to get a pulse of about 25mS to get things to work.

Now all I need to do is to get the complete circuit built up without using up to much board space.

Alan

yes um er that one

Just to let you know the 555 did the job. The encoder works brilliantly now. All I need to finish the project off is some concentric knobs for the encoder.

Thanks for the help.

Right of course.

Naki wrote:

QUOTE (Naki @ May 18 2009, 12:17 AM) <{POST_SNAPBACK}>

Right of course.

Paul ..... he forgot the Flux capacitor .... Naki how are we going to get home !