soft bypass , tru bypass that doesn’t hurt feet

Here’s an idea of mine . I became tired of 3PDT  mechanical switches . They’re a real pain in the ass to wire , they take time to be wired  and they break so easily (I broke few of them). The concept was pretty simple : I wanted a softer push button . Reducing cost was also in the idea . Therefore why not use a relay controlled by a momentary switch ?

you can’t really control the relay with only the momentary switch , a interface is needed . The fact is , with only the momentary switch the voltage to switch the transistor On will be remove as soon as you leave the button. A “memory” state is needed . I had in my stock 2 CD4093 Cmos chips . I made some researches and find a document using the same idea. I just modified few values and add a switch transistor to control the relay coil.

the original schematic :

and the tru bypass version


sof bypass

tested on breadboard , it works good . I modified the cap value for a smaller value (10n) . With the 470n the on/off was too long . To be clearer, if the button is pressed quickly few times in a short period of time the system doesn’t turn off and on as quick as you press the button. The 10n cap solved the issue.

No resistor for the LED ? there’s one , the DC resistor of the coil  ! a power regulator and a bigger cap on the 6Vshould be also nicer for the relay.

More deep experimentations could be considered to see the quickness of the switching and the possible rebounce of the switch . In pratical situation , it seems to work good . I’ll try to test it “in situation” loaded with a circuit. Unfortunatelly I’m not sure that will cure the famous “plop” tru bypass illness.

Actually you can use a lot different chips to have a similar circuit. A CD4017 for instance or a  4013 . The basic idea is a kind of “logic” circuit . You only need two states , on (or 1 ) or off (0). On will be V+ and off 0V . You don’t actually need a lot of voltage to turn the transistor on , juste go above 0.7V on the base for a Silicon transistor.

The drawback is obviously the additional chip on the circuit board and the current needed for the coil. In a pedal design it can be a thing to avoid. The cost won’t be really reduce by the use of a relay instead of the classic 3pdt. And you still need a mechanical switch , but it’ll stay cheaper that the 3pdts.

But on the other hand a shorter wirring time is obtained with a softer push button  which doesn’t need pressure to change its state , and it also has the tru bypass circuit !


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