I've been trying to create this simple radio buttons circuits out of hex inverters and diodes. I'd tried using 1N4148 and 1N4007 as a diode but I can't make this circuit to work as stated. Also I'm using a 5V supply since 7404 only works at
such voltage. Here the link of the circuit http://www.simplecircuitdiagram.com/2399-radio-buttons-using-push-on-switch-latching-circuit/ Thnks!

 

Hello,

I think that the circuit will not work with the 7404 TTL chip.
You could try the circuit with a 4049 CMOS chip.

Bertus

 

Sure looks like a good way to make a 30 - 50 Mhz oscillator......

Think about using an ATTINY and a small amount of Basic to do
this, debouncing the switches, as a proper way of doing this.

https://avrhelp.mcselec.com/index.html?debounce.htm

https://www.mcselec.com/

Regards, Dana.

 

Hello,

I think that the circuit will not work with the 7404 TTL chip.
You could try the circuit with a 4049 CMOS chip.

Bertus

HD74LS04P is only what I have on hand but I will try finding that IC and test if it works. Thanks~

 

I think you could get it to work with the 74LS04 by adding a resistor to each gate pair, like this :-

You may have to tweak the resistor value.

 

I think you could get it to work with the 74LS04 by adding a resistor to each gate pair, like this :-
View attachment 156338
You may have to tweak the resistor value.

I have tried doing this but only the second switch lathes on and doesn't switches off by itself but rather switches off when other switch is pushed and the two switches is always stayed HIGH on output.

 

What resistor value did you use?

the second switch latches on and doesn't switch off by itself but rather switches off when other switch is pushed

That is the correct operation of a radio button switch.

the two switches is always stayed HIGH on output.

That is not consistent with the first quote.

 

I think you could get it to work with the 74LS04 by adding a resistor to each gate pair, like this :-
View attachment 156338
You may have to tweak the resistor value.

The 74LS04 input current is 0.36mA with an input voltage of 0.4V.
This means R1 should be no more than about 1kΩ to insure that U2's input is low when U1's output is low.

 

Thanks for doing the math, Crutschow.

 

I think it's working now by somehow changing R1 into 1K ohm but would it be possible to add a reset button in order to set all the output to zero? Thanks!

 

would it be possible to add a reset button in order to set all the output to zero?

That's not how radio buttons work.

 

I think it's working now by somehow changing R1 into 1K ohm

That's good.
But for best reliability I would also add a 1kΩ resistor between the output of the second inverter and the input of the first inverter.
That way the output isn't fighting the input when the left diode tries to change the state of the latch.

would it be possible to add a reset button in order to set all the output to zero?

Yes.
Add a PB switch between V+ and R2 (in first schematic).

Edit: For your interest, here's an 8-button radio circuit that uses just two ICs and the push-buttons, no other parts.

 

That's not how radio buttons work.

Then call it radio push-buttons with reset.

 

That way the output isn't fighting the input when the left diode tries to change the state of the latch.
Yes.
Add a PB switch between V+ and R2 (in first schematic).

Thanks a lot! that solves my problem.

 

Just for reference, here's the LTspice simulation of the modified Radio Button circuit with reset using CD4049 hex inverters (thus one CD4049 package per 3 buttons).
The high input impedance of the CMOS inverters allows the resistors to be of higher value than used for the 74LS04 circuit.

The circuit draws only IC leakage current from the supply when quiescent so could be readily backed up with a battery and a couple diodes if the button state needs to be preserved during power down.

The circuit can be expanded to as many buttons as desired, of course.

 

Still looks like a lot of trouble when you can do it with one low-power MCU and no additional components besides the push-buttons.

 

Still looks like a lot of trouble when you can do it with one low-power MCU and no additional components besides the push-buttons.

Only for those who have the programming tools and know how to program, which is not trivial.
The circuit I referenced in post #12 requires only two standard ICs, no programming, and no additional components.

 

This could be done inside PSOC, the switches could be capacitive
touch (just pads on a PCB), and the switches would be debounced.

Additionally I think it can be done with no code. Zero external components
except for chip rail bypass cap.

But then it would be a shame to throw away the other 95% capabilities inside the PSOC.


Regards, Dana.

 

Here is a similar circuit I did for another thread. I've used variations of this for many years. This one has a transistor added to each output for LED or relay drive.

There is no debouncing on the switch make (when it is pushed) because the last bounce edge will latch the closed switch input. There is debouncing on the break (when the switch is released) so the last bounce edge doesn't latch an open-switch condition. The resistor network saves some assembly effort.

ak

 

One approach using mechanical buttons attached to pins,
one side, the other to ground. Using internal pullups on
input pins. Everything is onchip. Except buttons.



Or use Capsense to eliminate the buttons as well.


Regards, Dana.