I'm trying to implement a circuit that consist of 16 similar modules. Each module is a processed signal line which has to be routed into one of two outputs. Shure the SPDT is simple and rugged solution but I'd like to use tactile switch to choose which output the signal goes. And the switch has to remember its state after the circuit is off the power. Is there any way to implement this using DIP or SIP ICs? Thanks!
Please, don't blame me hard form my bad English )))
Analog STDP switch using tactile button with state control
integrated-circuitswitches
Related Solutions
I think your assessment that there are fewer N.C. type switches is somewhat short sighted. It is true that most TACT type switches are indeed N.O. type but many other switch types offer Form C type contact arrangements that offer both N.C. and N.O. on the same part.
If the input voltage on your regulator is always present you can leverage that to your advantage with some simple additional circuitry to provide the inversion logic that you require for use of a N.O. type switch. Here is how to connect it up.
Use an NPN transistor with its emitter connected to GND. Tie the collector to the inhibit pin on the regulator chip. Then connect a resistor from the base of the NPN to the input voltage supply rail. A 10K resistor may be a suitable value. Finally connect the N.O. tact switch between the base and GND. A small signal type transistor such as a 2N3904 is probably the best type to use.
Pressing the switch turns off the NPN which in turn frees the GND connection at the inhibit input.
If this is a battery-powered device then you're probably best putting a hard power switch between the 9V source and the rail to prevent leakage. This isn't an absolute fix - the battery will still have self-discharge and it prevents any standby operation for your uC. Ultimately it does depend on your application.
If you need standby operation then you either have to let the 9V source remain connected and active while the uC is in low power mode, or if your power usage is low enough you can put a huge capacitor on the power lines for the uC as a pseudo-battery backup. You'll probably want a diode to prevent the capacitor from discharging into the rest of the 5V rail in that situation. It also depends on what components the uC will need to have access to while in standby - can the IR sensor wake it up? It would need to be powered.
Also, it seems somewhat dangerous to include lightning in your circuit :)
Best Answer
Basically you want a 16PDT (electronic) switch. Look up analog multiplexers, that's how they're usually implemented. Here's for example the functional diagram from the datasheet of a 4PDT one:
You'll need use four of these.
You also need some additional memory circuitry to remember the state without power, like NOR flash, e.g. found in a microcontroler, if you want to completely avoid a mechanical way of remembering the settings.
And you can still find DIP packages for both analog multiplexers (e.g. BU4551 is the same type as the one above) and microcontrollers (e.g. ATMega328P aka arduino, or a smaller one like PIC12F617). You can find multiplexers with more (than four) channels on a chip, but usually not in DIP because they get large.