analogcounterdigital-logicmicrocontroller
I have a circuit with a 74ls93 counter and I want to use one of its outputs to switch between two analog output, i.e., when the output of the counter is HIGH, the output of the circuit must be V1 and when is LOW the output must be V2. V1 and V2 are fixed selected voltages between 0 and 5 V. The output of the circuit (V1 or V2) will be one of the inputs of a microcontroller.
What is the easiest and cheapest way to do this?. I think i need something like an analog multiplexer, but i'm not sure.
Easiest way is to use a telecom type relay.
All you need is a suitable relay driver.
They're fully characterized for the frequency range you're interested in (and well beyond).
Added in edit:
Since you need to switch quickly, something like this may work for you:
At 3ms it may be a bit marginal for 100Hz switching, depending on what exactly you're doing, but the 350usec (typical) models don't look too bad to me. You could always use a series/shunt arrangement if you need to increase the off attenuation.
A simple circuit can be built using a 4017 counter.
The circuit normally counts 10 input pulses but by connecting the next output to the reset input via a small signal diode (eg. 1N4148) the 4th count resets the circuit to 0. It also allows you to expand the circuit very easily.to more outputs if required.
Edit (additional)
As OQ requires change when switch or signal input goes low then the clock input needs to be inverted. This can be easily accomplished with a single PNP transistor. A 100R resistor has been added in series with the switch to prevent it getting 'sticky' when discharging the capacitor (see Spehro's comment).
Also added the 10k between D1 and C2/R3 to the original circuit.
Best Answer
Simplest and probably cheapest solution is to use 1/3 of a 74HCT4053, or use a 74HC4053 with a 4.7K pullup resistor on the 74LS output. Connect VEE to GND for this application.
A0 to V2
A1 to V1
AN is the output
S0 is the control input
/E should be grounded (to enable)
Unused inputs S1, S2 should be tied to GND or Vcc, the others can be left floating.