Help needed as CD4066 is not switching

Thread Starter

3pinplug

Joined Mar 17, 2022
13
Hi all
Hope someone can sadvise where i am going wrong, I am adding an FM detector boasrd to an AM radio via a switch at the point of the detector diode (copy of circuit attached - excuse my scribbliong hope this is ok) but i cannot get the CD4066 to switch back and forth, or actually even switch at all. I am only using two of the control pins and have put the other two to ground, have left the unused sig in / out pins as is.
Finding my way with this mod so hopefully I haven't gone way off track, it was going well until I got to the CD4066 as not used one in a circuit before.
many thanks
Mark
cctdark0004.jpg
 
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Thread Starter

3pinplug

Joined Mar 17, 2022
13
Hi
The supply voltage (Pin 14) for the cd4066 is at 9v at present, when you mention "voltages" which ohers do you require and I will have a measure.
Thank you to all for the very prompt replies and link to the datasheet, much appreciated.
 

bertus

Joined Apr 5, 2008
21,896
Hello,

Is pin 7 connected to ground?
4066_pinout.png
What are the input levels for the control voltage?
In the datasheet this is given :
Normal operation control-line biasing: switch on (logic 1), VC = VDD; switch off (logic 0), VC = VSS

4066_control.png
See the datasheet for more info.

Bertus
 

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eetech00

Joined Jun 8, 2013
3,154
Hi
The supply voltage (Pin 14) for the cd4066 is at 9v at present, when you mention "voltages" which ohers do you require and I will have a measure.
Thank you to all for the very prompt replies and link to the datasheet, much appreciated.
What is the max pk-pk voltage being switched thru the 4066?
You'll need dual supply voltages for the 4066 or bias the sinewave i/o thru the 4066.
The switch control inputs will also need to be pulled up or pulled down.
 

Thread Starter

3pinplug

Joined Mar 17, 2022
13
HI all
I will attempt to answer the questions above as best I can:-
1. Yes Pin 7 is grounded.
2. Control voltage for Ctrl A & B i set at 5V, simply connected it to a 5 V feed hope that is the way to do it.
3. Ctrl Inputs pulled down - the two unused control inputs I conencted to ground as not being used, corrsponding Input output pins I have done nothing with.
4. Max Pk to Pk voltage - can you expand please as I am still learning i.e where I would measure that, (Sign wave Peak - Peak?) but sure where I am measuring this on the circuit.
Thanks again for your help with this.
 

eetech00

Joined Jun 8, 2013
3,154
3. Ctrl Inputs pulled down - the two unused control inputs I conencted to ground as not being used, corrsponding Input output pins I have done nothing with.
not shown on your schematic .

4. Max Pk to Pk voltage - can you expand please as I am still learning i.e where I would measure that, (Sign wave Peak - Peak?) but sure where I am measuring this on the circuit.
Thanks again for your help with this.
The 4066 appears to be switching a bi-polar signal, ie, an audio signal. So...to switch this signal, the 4066 has to have bi-polar supplies of a voltage level at least the equivalent to the max pk voltage of the audio signal. If the signal is small enough, you might be able to bias the signal at some level to allow it to be switched.
peak to peak voltage shown below.

1647536517467.png
 

Thread Starter

3pinplug

Joined Mar 17, 2022
13
Apologies all as highlighted missed showing the two unused ctrl pins to ground on the schematic.
EEtech Do i need to measure the audio signal with my scope at the detector diode for the peak-peak reading?
 

crutschow

Joined Mar 14, 2008
29,792
For a CD4066, the signal peaks can not be greater than the plus and minus supply voltages for the CD4066.
Also the control signal should be equal to the plus and minus supply voltages for proper switching.
 

eetech00

Joined Jun 8, 2013
3,154
Apologies all as highlighted missed showing the two unused ctrl pins to ground on the schematic.
EEtech Do i need to measure the audio signal with my scope at the detector diode for the peak-peak reading?
Measure from each 4066 switch input used to switch the signal to the signal ground reference (where ever that is).
 

Thread Starter

3pinplug

Joined Mar 17, 2022
13
Hi all
Little confused at mo with the 'peak to peak' and where I should measure it at :-i.e
1.VDD
2. Particular Control pin
3. Sig in pin
4. At the dteector diode (before or after)?
5. or somehwere else? T
To answer the post above, the power for the CD4066 is just applied to Pin 14, notice on the PDF above ground is shown as the "Low Power Pin" - should Pin 7 be ground or should I have some power there.
I will get there honest!
 

Thread Starter

3pinplug

Joined Mar 17, 2022
13
Ok great, I will measure in the morning as have visitors arriving shortly and report back with the readings.
Thank you to everyone who has posted so far, really appreciate it.
Have a good evening all.
 

Thread Starter

3pinplug

Joined Mar 17, 2022
13
Hi all
Measured the signal at Input 1 and Input 2, results as follows for Peak to Peak:-

Input 1 = 120mv Peak - Peak
Input 2 = 95mv Peak - peak
Also attach my scope traces although its very bright and they didn't come out that well.

Just seen the 5th post above, so I need the "Control Voltage" and "Supply Voltage" to be exactly the same voltage say 9 Volts and it should work, ok I will try that and report back as well.
 

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