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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #11  
Old 01-11-2011, 03:18 PM
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Bernard Bernard is offline
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Welcome back. I' drawn up amy interpitation of your requirement- at least something to throw knives at. As shown big AND gate uses jumper wires, but could easily use dip sws & still provide for necessary inversions by directly connecting U2 outputs 8- 512 to invertor inputs, outputs going to
dip sw's. That is just one more 74C14 [ or other invertor ] for 2- 8 position dip sw's. Assuming not using 1,2.4,&2048. I would preffer moving diodes to U15 side of AND.
Rather than inhibiting U2 input, U2 reset is held hi when ckt is off. The F-F is composed of U9 & U10. Pushbutton sw , SW1,starts water flow by setting F-F , U9-Q hi & removing reset from U2. When programed count is reached, U2 is reset & & U8 receives a count. U8 counts up, illuminating LED's in sucession, untill SW3 selection is reached, U8 clock enable goes hi stopping further counting; selected LED stays on, F-F is reset, valve closes, U2 held at reset. A manual reset is provided by SW2.
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  #12  
Old 01-11-2011, 03:44 PM
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The CD4040 is a ripple counter, not a syncronous counter. Its ripple causes many extra glitch outputs that will probably clock the CD4017 wrongly.

Maybe the timer circuit should be a simple CD4541 oscillator/timer IC instead of those hundreds of parts.
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  #13  
Old 01-11-2011, 04:46 PM
SouthernAtHeart SouthernAtHeart is offline
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Quote:
Originally Posted by Audioguru View Post
The CD4040 is a ripple counter, not a syncronous counter. Its ripple causes many extra glitch outputs that will probably clock the CD4017 wrongly.

Maybe the timer circuit should be a simple CD4541 oscillator/timer IC instead of those hundreds of parts.
Doesn't the 4541 create it's own pulse/freq. rather than monitor the incoming pulses?
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  #14  
Old 01-11-2011, 04:51 PM
SouthernAtHeart SouthernAtHeart is offline
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Quote:
Originally Posted by Bernard View Post
Welcome back. I' drawn up amy interpitation of your requirement- at least something to throw knives at. As shown big AND gate uses jumper wires, but could easily use dip sws & still provide for necessary inversions by directly connecting U2 outputs 8- 512 to invertor inputs, outputs going to
dip sw's. That is just one more 74C14 [ or other invertor ] for 2- 8 position dip sw's. Assuming not using 1,2.4,&2048. I would preffer moving diodes to U15 side of AND.
Rather than inhibiting U2 input, U2 reset is held hi when ckt is off. The F-F is composed of U9 & U10. Pushbutton sw , SW1,starts water flow by setting F-F , U9-Q hi & removing reset from U2. When programed count is reached, U2 is reset & & U8 receives a count. U8 counts up, illuminating LED's in sucession, untill SW3 selection is reached, U8 clock enable goes hi stopping further counting; selected LED stays on, F-F is reset, valve closes, U2 held at reset. A manual reset is provided by SW2.
I'm following most of this,
I'll be drawing this up in PCB Artist! I'm not quite sure about the inverters, if/why I need them if I use DIP switches, but I'll post my drawing thus far when I get it done.
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  #15  
Old 01-11-2011, 06:28 PM
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Originally Posted by SouthernAtHeart View Post
Doesn't the 4541 create it's own pulse/freq. rather than monitor the incoming pulses?
The CD4541 has its own built-in oscillator but can also use an external oscillator. It is a timer that is programmable with DIP switches or other things.
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  #16  
Old 01-11-2011, 08:58 PM
SouthernAtHeart SouthernAtHeart is offline
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Originally Posted by Audioguru View Post
The CD4541 has its own built-in oscillator but can also use an external oscillator. It is a timer that is programmable with DIP switches or other things.
I am drawing up something now, with the ripple counter, and will post what I got tonight. If it seems better to use the 4541, I don't mind that. I tried finding some schematics with the 4541 in it so I'd better understand it, but anything I found, it was being used as an oscillator/timer like thing... If it's not hard to sketch a diagram or if you could point me to an example online somewhere, I'd like to see it.
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  #17  
Old 01-11-2011, 09:26 PM
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I do not think ripple counter glitches are a problem, but threw in a glitch filter just in case. I do not see a way around using invertors to decode random number selection.
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  #18  
Old 01-11-2011, 09:42 PM
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The CD 4541 does not look verry promising if I read it right- selects only 4 divisions??
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  #19  
Old 01-11-2011, 10:04 PM
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The CD 4541 does not look verry promising if I read it right- selects only 4 divisions??
Then use a CD4536 oscillator/timer IC. It has 24 binary counter stages. Its first 8 stages can be bypassed with one-bit and its last 16 stages can be decoded with 4-bits.
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  #20  
Old 01-11-2011, 11:03 PM
SouthernAtHeart SouthernAtHeart is offline
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Default My first draft

Quote:
Originally Posted by Bernard View Post
I do not think ripple counter glitches are a problem, but threw in a glitch filter just in case. I do not see a way around using invertors to decode random number selection.
Here's a .pdf of what I've got so far. I didn't put in the inverters, but I will if you say I need them. I thought that if any of the dip switches were open, then that leg would just read high? I must not be following the logic quite right here.

Note that I've added a 3 digit display to give a readout of the cups as the water fills up. If I decode the pulses into 10th's of a cup (1/10 of 6 oz to be exact) then the display will count to the 10th's decimal place! That should be pretty nice.

Oh, I see a mistake already. The output going on the the cup counter is counting 10th's of a cup, not cups. I guess I need to put another devide by 10 (4017) in there, unless I find some kind of smaller chip with fewer pins.

Can someone also confirm that the BC548 transitor is a good choice to gate the water solenoid-I don't quite follow the PNP/NPN thing.


I'll now work on adding the glitz remover components you just mentioned...
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