Hi, iam in need of adding an additional 2s delay to a 555 controlled timer circuit.
Mostly it should work like - when power in on, initial 2s delay, then 555 timer will turn on relay for 1s, then goes off for 4s, again on for 1s, off for 4s and goes on.
Can anyone help me implementing this circuit without using additional 555 timer for initial 2s delay?
Also i would appreciate if you can help me with the diagram of 1s on 4s off relay circuit using 555 timer.
Thank you.

 

1)Try connecting the timing capacitor to V+ instead of V-. Then it will start with the output low.
or
2) If you connect the relay coil between pin3 and V+, then it is easy. You just need RA to be 3 x Rb, and it will give 4 seconds high, 1 second low.
It will also start with the high period which is what you wanted, but he initial off period will be longer than 2 seconds - will that be a problem?

 

1)Try connecting the timing capacitor to V+ instead of V-. Then it will start with the output low.
or
2) If you connect the relay coil between pin3 and V+, then it is easy. You just need RA to be 3 x Rb, and it will give 4 seconds high, 1 second low.
It will also start with the high period which is what you wanted, but he initial off period will be longer than 2 seconds - will that be a problem?

initial delay is intended to be 2s, as the circuit gonna be used in windshield wiping,
So it should be like, when power is on, initial 2s delay, then turning on the relay for 1 second, then goes off 4 second, then on for 1 second, off for 4 second.
Initial delay is kind of like RC delay, but trying to figure out how to achieve this without using additional 555 timer.
If you share circuit diagram or any resource it will be helpful.
Thank you.

 

For windshield wiping I wouldn't have thought it mattered much whether the initial delay were 2s or 4s ?

 

I would have gone for No delay. After all, how often do I look through the windscreen and think “this will need wiping in 4 seconds time”?

 

As I understand it - a windshield wiper motor unit has three wires: One for chassis ground, one for power and one to park the wiper. The "Park" feature insures the motor runs till the wiper blade is fully in the down position. When the car is running the Park feature is always powered. But the motor doesn't run because of an internal switch that parks the wipers is held open (in the park position) so the motor doesn't run. The main power wire only runs the motor when you turn the wipers on. As long as there's main power the wipers run. When you shut the wipers off, without the park feature, the wipers would stop wherever they were when you shut them off. That's where the park feature comes in. That internal switch maintains power to the main power line until the wipers park.

If you were to power the main power line for a quarter second, assuming the wiper takes a full second to complete one cycle then the park feature will make sure the wipers park every time. All you need is to bump the main power for a quarter second and the wipers should go into a full cycle sweep of the windscreen. Your circuit will just need to jump the park wire to the main power for that brief moment. Then using a pot and a 555 timer all you need to do is pulse that jump circuit (probably a small relay) and you have intermittent wipers. The pot would control how frequently the wipers cycle. Every 2 seconds, 2 1/2 seconds, all the way up to once every 10 seconds. Or longer if you prefer.

Like others I don't understand why you need the wiper to delay by two seconds before starting. If during startup if the windshield needs wiping - let it wipe. If you're driving and encounter a light sprinkle you turn the intermittent circuit on when you feel it necessary.