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Circuit of the switch 12v. led-lighting

rjenkinsgb

Well-Known Member
Most Helpful Member
The circuit should work OK.
But: Remember one of the most basic engineering principles - KISS - Keep It Simple, Stupid!

How is that circuit in any way more functional or more advantageous than using the switch to directly control the relay coil - or indeed, control the lamp circuit directly?

As an educational project it is a novel application, but I do not see it to be more than that?
 

kaspiysk113

New Member
The circuit should work OK.
But: Remember one of the most basic engineering principles - KISS - Keep It Simple, Stupid!

How is that circuit in any way more functional or more advantageous than using the switch to directly control the relay coil - or indeed, control the lamp circuit directly?

As an educational project it is a novel application, but I do not see it to be more than that?
The scheme is assembled by me and works perfectly.
Of course, it is no more functional or profitable than what you mentioned.
This goal was never set.
The goal was to make the light switch controlled by a single button with a return to the original position. The goal was also to make a small and aesthetically pleasing switch.
So, the principle of "KISS", I believe, was taken into account, thank you for reminding me.
 

Pommie

Well-Known Member
Most Helpful Member
I've still no idea what it does as you've never told us. And, I'm not willing to work it out.

Mike.
 

AnalogKid

Well-Known Member
Most Helpful Member
I've still no idea what it does as you've never told us. And, I'm not willing to work it out.
The circuit converts an SPDT pushbutton switch to alternate-action. U1A is a set-reset flipflop to debounce the switch, and U1B is a toggle flipflop that drives the output stage.

There is a problem with all of the Set and Reset inputs. This would be more apparent if you drew a schematic instead of a wiring diagram. A correct schematic has separate symbols for each flipflop with the inputs and outputs arranged in a traditional manner, not the physical package. This makes its possible for any experienced viewer to see the intent of the design. Redraw the schematic and you will see the problem. Yes, the circuit works, but not by design.

See figure 3 of this datasheet for the correct schematic symbols.

ak

ps. Ground symbols never point any direction but down. Antennae and power symbols point up; grounds point downward, always.
 
Last edited:

kaspiysk113

New Member
The circuit converts an SPDT pushbutton switch to alternate-action. U1A is a set-reset flipflop to debounce the switch, and U1B is a toggle flipflop that drives the output stage.

There is a problem with all of the Set and Reset inputs. This would be more apparent if you drew a schematic instead of a wiring diagram. A correct schematic has separate symbols for each flipflop with the inputs and outputs arranged in a traditional manner, not the physical package. This makes its possible for any experienced viewer to see the intent of the design. Redraw the schematic and you will see the problem. Yes, the circuit works, but not by design.

See figure 3 of this datasheet for the correct schematic symbols.

ak

ps. Ground symbols never point any direction but down. Antennae and power symbols point up; grounds point downward, always.
Thank you for your comments about the symbols in the diagram, I will keep this in mind in the future.
I have a scheme based on separate function blocks, but I don't see any problems with the “set” and “reset”inputs on it.
What exactly do you mean?
 

kaspiysk113

New Member
This same chip was previously used by me to repair the DGT Easy chess clock.
This watch failed to switch time, and the crossbar was not held clearly in one of the positions.
The problem was solved by using the built-in R#/S# triggers in hc74.
If it is interesting, I can publish it on this forum.
 

ChrisP58

Well-Known Member
Unless you've already got +5V elsewhere in the system, I'd suggest changing the 74hc74 to a CD4013B flip-flop. The CD4000 series can run on 12 volts, so you wouldn't need a separate 5 Volt regulator. Be aware though, that the logic state of the S and R inputs are different between the hc74 and the 4013. Also the pinouts are different.

Also, I would eliminate the relay by using a mosfet to drive the LEDs.
 

kaspiysk113

New Member
Unless you've already got +5V elsewhere in the system, I'd suggest changing the 74hc74 to a CD4013B flip-flop. The CD4000 series can run on 12 volts, so you wouldn't need a separate 5 Volt regulator. Be aware though, that the logic state of the S and R inputs are different between the hc74 and the 4013. Also the pinouts are different.

Also, I would eliminate the relay by using a mosfet to drive the LEDs.
Thank’s Cris !
these are great notes on the circuit, but it's just that I came from the chips I have, so I used hc74
and the relay is also needed as a sound sounder, I was interested in its click when switching
 

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