Frequency Meter Function Control?

[hadihf]

cd4066 touch switch project

Hi,

I have a circuit for I/n/t/e/r/s/i/l 7216A frequency counter. However the gate and range selection is done via rotary switches. I need a circuit to do all this switching digitally with two momentry switches with leds indication of gate time (0.1s, 1s, 10s) and range (10Mhz, 50MHz, 500MHz). Please somebody can help?

Regards

 

[Buriedcode]

Hi,

I've just had a quick look over the datasheet for the 7216A, and I see that the application circuit has 2 'rotary' switches, and 4 'dip' switches. Looking at the block diagram, it 'looks' like there are only logic signals flowing through the switches, no analogue. so I think that a couple of multiplexers will do, controlled, either by a microcontroller, or with a binary counter (with a push switch as the clock to increment it).

Some IC's you could use are.. 74HC150, 74LS151 , 74LS153 - a dual 4-1 multiplexer.
Although, whether you use a 'multiplexer' or 'demultiplexer' depends on which way the signals flow.

You could also use some small FET's, each as a switch, which allows current to flow both ways. These can then be controlled by a decade counter (4017B?), which is incremented via a push switch (effectively, acting like a rotary switch, with one push button sequentially seletecting each fet). This could also give you the LED's, since the output from the decade counter could drive both the FET and an LED. It really depends on cost, size, and complexity of the circuit you want.

Of course, you would need two of these circuits, since there are two 'rotary switches' needed. I would say, give the multiplexer/demultiplexer thing a go, it'll be less complicated, but may not work. If you have already build the frequency counter circuit, check which are the inputs and which are outputs to and from the rotary switches, using diodes.

If you are struggling, then I could draw up a quick dirty schem to show you exactly what I mean.

Good Luck,

BuriedCode.

 

[IanP]

I don't think you need multiplexers and/or demultiplexers ..
To select "range" and "functions" UP and DOWN you need UP/DOWN shift registers (4-bit for ranges and 6-bit for functions) and CMOS switches such as for example CD4066 ( https://www.fairchildsemi.com/ds/CD/CD4066BC.pdf ) to connect required 7216A pins ..
However, I would suggest that you consider the use of a reduced-pin microcontroller, such as for example 89C2051 or a PIC, and program the required logic in it.
The CMOS bilateral switches still will be required to execute selected option(s), but the beauty of this solution is that hardware remains always the same, and if you make a mistake in logic, you can always correct it and re-program the microcontrller again and again, till you are happy with it ..

Regards,
IanP

 

[hadihf]

Well I was asking for a working circuit actualy. I am attaching the current working FC... this is a sensitive and trouble free circuit and in service for 7 years. As one can see that gate amd range selectionis is done with push switches. A logic switching will be be a nice touch. Complete project (Schematic, PCB etc) will be posted with new switching.

Regards

 

[Buriedcode]

Hi,

A working circuit eh? Sorry, I was just spouting idea's. Basically, replacing the switches with 'electronic' switches that can be controlled with logic so you can attach it to your existing design. As I said in my earlier post, it can be done in pure logic or microcontroller.

Complete project (Schematic, PCB etc) will be posted with new switching.

Excellent, look forward to seeing what route you've taken.

BuriedCode.

 

[hadihf]

Additional features can be added using a pic control...

1- 1/10 att.(using a relay)
2- Low pass filter
3- Threshold control

7 years ago I had time to do such things...now I am old and lazy.

Regards