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 Forum index » DIY Hardware and Software
cheap and easy cv quantizer
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zipzap



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PostPosted: Mon Dec 11, 2006 2:13 am    Post subject: Reply with quote  Mark this post and the followings unread

CMos chips don´t like their inputs to be not connected. Stuff like chaotic counting will happen. It´s not like they react on high or no voltage. It needs to be clocked with high and ground. maybe that´s the problem.
Like say, you have the counter, and the clock is connected via a diode. Then you need a resistor, 10k-100k from the input to ground, to keep it low when no high signal is applied. That´s called a pulldownresistor.

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blue hell
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PostPosted: Mon Dec 11, 2006 4:55 am    Post subject:
Subject description: follow up:
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fonik wrote:
the 4516s are the problem, they count erratically with no clock connected either! ( i tried different ICs!). Shocked


Just to be sure .. do you have floating inputs maybe ? For cmos all unused inputs should be tied to either + or gnd otherwise the device will show strange behaviour.

edit : I just had this happening on my desk, forgot to make an unconnected processor pin output resulting in erratic interrupts ...

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also .. could someone please turn down the thermostat a bit.
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fonik



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PostPosted: Mon Dec 11, 2006 5:08 am    Post subject: Reply with quote  Mark this post and the followings unread

hi guys, thanks for taking care again.
i clock the 4516s with my doepfer LFO (using the positive pulse output). the clock does not seem to have any effect anyway. i left of the pins 2 and 7 of the first 4516, according to schematic. should i try to tie them to ground?

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PostPosted: Mon Dec 11, 2006 6:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Embarassed had not seen zipzap's earlier reply.

Pins 2 and 7 are ouputs and should not be connected.

What level does the pulse have you connect to the clock input ? It should not go higher than the supply voltage of 4516 and it should not go below zero. If not you might blow the chip.

Sorry if this had been discussed already.

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also .. could someone please turn down the thermostat a bit.
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fonik



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PostPosted: Mon Dec 11, 2006 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

any help, suggestions or comments highly appreciated!
the clock pulse goes from 0V to approx 5V, quite below supply voltage. the 4516s show the same strange behaviour with or without clock - i don't know...

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Uncle Krunkus
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PostPosted: Mon Dec 11, 2006 7:09 am    Post subject: Reply with quote  Mark this post and the followings unread

They show the same erratic behaviour with or without clock. What happens if you tie them low/high? Have you tried a different clock source? ie: a 555 running off the same supply? They're erratic with nothing connected, that makes sense. So does the output of the doepfer "look" like a floating signal to the 4516? I don't know. Just throwing around some ideas. Good luck Fonik. They are just modified grains of sand! They can't beat a rational, analytical mind!
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blue hell
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PostPosted: Mon Dec 11, 2006 7:25 am    Post subject: Reply with quote  Mark this post and the followings unread

According to http://www.jaycar.com.au/images_uploaded/MC14516B.PDF :

for a supply voltage (for the 4516) of 10 Volt

VIL = < 3V .. 4.5V
VIH = > 5.5V .. 7V

for a supply voltage of 15 V

VIL = < 4 .. 6.75 V
VIH = > 8.25 .. 11 V

VIL is the voltage that is guaranteed to seen as a low by the 4516 and VIH likewise the voltage guaranteed to be seen as high. Thes volatge change with the supply voltage of the device.

I don't know what the supply voltage is exacly, but it seems that a 0 .. 5 V input signal is almost giaranteed to be not ever seen as a high input signal by the 4516.

This should however not lead to erratic behaviour, it should just not work.

Edit : as said by Uncle K, unconnected clock inputs will indeed lead to strange behaviour.

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fonik



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PostPosted: Mon Dec 11, 2006 10:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
for a supply voltage of 15 V

VIL = <4> 8.25 .. 11 V


you shed some light on a dark place... i just checked the output voltage of the LFO i am using as clock (or even trying to use) and it goes from 0V up to 7.8V. i am powering the circuit with 15V so this might be the crux!? it's neither high or low, it's just inbetween...
unfortunately i have a baby10 sequencer on my one and only breadboard for this week. so i will see what i can use as clock (a 555 maybe?).
anyway thanks again. a really good pointing...

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PostPosted: Mon Dec 11, 2006 11:48 am    Post subject: Reply with quote  Mark this post and the followings unread

When you wouldn't mind the clock to invert you could prepend a simple one transistor circuit to make anything above let's say 2.3 V to be active while protecting the input for voltages under zero and above 15 Volt.

Like below (just a suggestion of course).

Code:



                  0--------------------0-------o + 15V
                  |                    |
                ==^==                 .-.
                 / \  SI              | |10K
                .---.                 | |
                  |                   .-.
                  |                    |
                  |                    0-------0 OUT
                  |                    |
         470 E    |   10 K             | C
        .-----.   |  .-----.     B  | /
IN 0----|     |---0--|     |--0-----|<   NPN
        .-----.   |  .-----.  |     | \
                  |           |        | E
                ==^==        .-.       |
                 / \  SI     | |3K9    |
                .---.        | |       |
                  |          .-.       |
                  |           |        |
GND 0-------------0-----------0--------0-------0 GND



Not sure how to make an emitter in ascii art, but hope it's clear this way :)

The SI diodes could be almost anything made out of silicon, the transistor would have to be some general purpose NPN thingy, almost anything would do here as well as long as it's not a power transistor (I assumed HFE to be > 100).

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fonik



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PostPosted: Mon Dec 11, 2006 12:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

cool Cool

allways learning... thats good

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