Addition of Intermittent Wiper mode for Hyundai i10 ERA

My Hyundai i10 ERA model does not have an intermittent (slow periodic) wiper mode. This is useful during light drizzle where a lowest speed continous wiper operation is not necessary and may cause noizy wipes. This project intents to add the intermittent wiper operation feature to the car without much intrusion to the electrical system. This may be used for other cars also that does not have this mode.

To implement the intermittent operation, we need to understand the wiper operation. The wiper motor circuit has a permanent positive supply through the ignition switch. This is required because the circuit need to supply the current to the motor for a complete back and forth sweep. Even if the wiper is switched off during a wipe, the motor still operates till the arm comes back to the parking position. However if the ignition switch is turned off between a wipe, the wiper arm will be frozen (try it out). Thus the wiper has the circuit to guarentee a minimum of one cycle operation, even if the wiper switch is activated only for a fraction of period (of one cycle). This project relies on this feature.

Now, my car has these wiper modes on the stalk: Instant, Slow speed, High speed. This project adds an intermittent operation to the existing stalk with the existing switches.

This circuit sits between the Instant mode switch line and the wiper relay. For the driver, whenever he wants intermittent operation, he just taps the instant wipe. The circuit operates the wiper in a delayed mode. Whenever the driver wants to switch off the wiper, he just taps the instant wipe again.

Here is a description of the circuit operation:
When the Instant mode is activated, the circuit senses switch ON and initiates a delay counter. At the same time output is also made ON till the instant mode is held. The counter resets after a certain delay time and the circuit outputs another ON to the relay. The counter is reset and the process repeats. Note that the driver had initiated the Instant mode only once. Now, to stop the intermittent operation, the driver makes an activation of the instant mode. The circuit senses the input and stops the outputs.

Input vs Output Timing diagram of the circuit:

Block diagram:

This is the simplest mode of operation. Now we need to add a couple of features to the circuit. We are now depriving of the original instant mode. So if the driver wants to have a single instant wipe, he need to activate the mode twice - one for ON and the second for OFF. This can be a fast operation also, which is sensed by the circuit.

This is a fixed delay circuit now. What if we wants a variable delay mode? Can the driver specify the delay also while switching on? Can the second input measure the delay between the wipes?