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 Forum index » DIY Hardware and Software
cd4066b bi lateral switch problem
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anclib



Joined: Oct 12, 2012
Posts: 11
Location: UK

PostPosted: Tue Apr 01, 2014 10:31 am    Post subject: cd4066b bi lateral switch problem Reply with quote  Mark this post and the followings unread

Hello, please help.

I currently am having problems getting my project working which is a drum sequencer.

I have a wav trigger board, which has 16 inputs to trigger wav sounds, I have a matrix of push latch switches on a board and a CD4015 creating the sequence.

On each step I have taken an output from the CD4015 and fed it to the corresponding row of switches, then this feeds to a CD4066 to drive the wave trigger board input switch.

My problem is that the CD4066's seem to be turning on and off at random, but when I ground out the earth supply to the cd4066's with my hand it seems to work better, but not 100%.

A few possible things I think could be causing this are:

1. not enough voltage going to the switch board and feeding through to the 4066's
2. some sort of ground problem or back voltage problem
3. noise in the inputs to the 4066s

I just thought I would ask the community before digging in headlong.

I have a load of lm324s so I was thinking maybe boosting the input signals coming from the switch board.

Any help is very much appreciated.
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PHOBoS



Joined: Jan 14, 2010
Posts: 1647
Location: Moon Base
Audio files: 332

PostPosted: Tue Apr 01, 2014 12:24 pm    Post subject: Re: cd4066b bi lateral switch problem Reply with quote  Mark this post and the followings unread

hmm a schematic would be very useful here.

Quote:
I have a wav trigger board, which has 16 inputs to trigger wav sounds

What kind of inputs are they. Do they need a trigger voltage or is it like a switch contact you could connect something like a pedal to ?
Did you connect the control inputs of the 4066 directly to the 4015 or do you have the switches in between ? If so did you use any pulldown
resistors or do they float when the switch is open ?. Do you have any (other) inputs floating ?

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anclib



Joined: Oct 12, 2012
Posts: 11
Location: UK

PostPosted: Tue Apr 01, 2014 1:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

I haven't really got a schematic, I'll try and upload something when I get a chance.
there are a few pictures in the attached zip file

there are no pull down resistors so I suppose they are floating, I thought that as long as there was no voltage input there would be no switch in the 4066.

the wav trigger can be set to accept a voltage trigger or set to a switch contact, there are male headers on the board half of which are ground.


drum sequencer project.zip
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Tue Apr 01, 2014 6:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Adding some pulldown resistors to the control inputs of the 4066 will most likely solve your problem. If the inputs are left floating the state is
undetermined. And the inputs are very sensitive to noise especially with the wires acting as antenna's. This can actually be fun to play with like a sort of
theremin but probably not what you want right now Wink

nice wavplayer btw Razz

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bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Wed Apr 02, 2014 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

yeah, id go for pull down resistors on the inputs of any cmos based IC's as standard which will probably solve your problem here too Smile
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anclib



Joined: Oct 12, 2012
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PostPosted: Wed Apr 02, 2014 6:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi thanks for your help.

any idea of the pull down resistor value? hi/low? or will anything do?
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bubzy



Joined: Oct 27, 2010
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PostPosted: Wed Apr 02, 2014 7:24 am    Post subject: Reply with quote  Mark this post and the followings unread

i use 100k for pullup/downs
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PHOBoS



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PostPosted: Wed Apr 02, 2014 7:30 am    Post subject: Reply with quote  Mark this post and the followings unread

100K is good value but it's not very critical. I've seen pulldown resistors ranging from 1K to 10M.
(low values use more current while high values make it more sensitive to noise)

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