Intermittent wiper circuit

[LouCi4er]

Hi guys,first post here.I wanted to build an intermittent relay for my truck.After several attempts to build something by my own,i finally bought a Smart Kit No1093.I thought that it is what i was looking for but not quite what i was waiting it would be.Anyway,i assembled it very easy tried to connect it to my car but here it comes.The circuit has fixed on and off times.If i increase the on time,the off time becomes equal as the on time.I thought that it will adjust only on time but i was wrong.Now i want to leave fixed one time but be able to adjust the other.What do i need to add or replace to achieve that?Does anyone have any experience with this circuit?

Thanks in advance.

If you need the schematic,let me know.

 

[LouCi4er]

These are the parts:
R1, R2, R5………3,9KΩ 1\4 W
R3……………….6.8KΩ 1\4 W
R4……………….47KΩ 1\4 W
D1, D2…………..1N4148
D3……………….1N4001
C1,C2……………….100μF\25V
Q1……………….BC548
U1……………….LF351 ή TL081
K1.........................ρελέ
P1.........................470KΩ lin

and the schematic:https://www.quasarelectronics.co.uk/kit-files/smart-kit/1093.pdf

 

[alec_t]

The circuit has fixed on and off times

I don't see how. The on time is fixed at about 0.5 sec but P1 should vary the off time from about 3.5 sec to 35 sec. If it doesn't, then something is incorrect in your circuit as built.

 

[KeepItSimpleStupid]

Let's be realistic here: 10 to 60x per second. When was the last time you saw a wiper blade sweep 60 times in 1 second. Even a 1 sweep per second is long.

So there are at least two ways wipers can work. They can have a separate park function. These are annoying. In a FORD I owed way back when, turning off the switch would instantly reverse the direction without completing the sweep. In the FORD, the park logic was part of the wiper switch. One car the family owns makes the same length sweep, but with different start points. You also have low and high speeds to deal with.

"Generally" you can pulse the wiper switch and the wiper motor takes care of the rest. So, think of a 1 second pulse occurring at some rate from say 10 to 60 seconds using the low speed winding for intermittent. The design is not as simple as it seems.

 

[LouCi4er]

I don't see how. The on time is fixed at about 0.5 sec but P1 should vary the off time from about 3.5 sec to 35 sec. If it doesn't, then something is incorrect in your circuit as built.

Well,you are right.If i connect the pin 4 and the pin 5 it is working as you discribe it.On time at about 0.5 sec and P1 vary the off time.The on-off times are equals if the pin 4 are seperate from pin 5.The problem is that 0.5 sec is not enough for the wipers.The motor needs at least 1 sec(2 would be perfect) so it would be able to complete the cycle through the parking system.Can i increase the on time from 0.5 sec to 1 or 2 sec?

 

[LouCi4er]

Let's be realistic here: 10 to 60x per second. When was the last time you saw a wiper blade sweep 60 times in 1 second. Even a 1 sweep per second is long.

So there are at least two ways wipers can work. They can have a separate park function. These are annoying. In a FORD I owed way back when, turning off the switch would instantly reverse the direction without completing the sweep. In the FORD, the park logic was part of the wiper switch. One car the family owns makes the same length sweep, but with different start points. You also have low and high speeds to deal with.

"Generally" you can pulse the wiper switch and the wiper motor takes care of the rest. So, think of a 1 second pulse occurring at some rate from say 10 to 60 seconds using the low speed winding for intermittent. The design is not as simple as it seems.

Agree.Wiper's circuit or better,harness is more complicated than most people think.It is a combination of the motor-harness-switch.I found it the hard way.The only thing needed is a circuit that will be able to produce a 2 sec pulse every x time where the x would vary by a potensiometer.Nothing more.

 

[KeepItSimpleStupid]

Nothing more.

Maybe maybe not. In one case I could envision is using high and low to disable power to the intermittent control. One also assumes that power is switched by the wiper switch.

Back in the mid 70's I tried to do this on a 60's vehicle. But because it was that FORD, it was impossible. Well may not impossible, but beyond my capabilities at the time.

So, what actually happens when you turn on the wiper switch briefly?
Some options:
1) It returns to park immediately
2) It completes one cycle

-- A little story. I was driving down a back road and suddenly my headlights started to blink at a consistent rate. What happened?

 

[LouCi4er]

One day i was driving my car with 140 kmh.At a turn i released the throttle,after the turn i pressed it again but nothing happened.The car was dead,it was only slowing down.After a couple attempts,all the sudden,it came back to life.This was 5 months ago and it never did that again.What happened?

You are talking about(the FORD) a very old car.My truck is '98 model.When you turn the wipers on,the switch connects the ground and the first speed of the wiper motor.The +12 is connected to the motor from the key switch.So the wipers are moving.When you close the wiper switch,it connects the first speed with the parking wire which supply ground by a circular contact inside the worm gear reduction of the motor.It is very simple disign.This picture will help a lot.

 

[KeepItSimpleStupid]

Vapor lock in your case? The headlight problem was the bulb failed shorted and had a thermal breaker.

My question about your wiper is if the dash wiper switch is simply 3 wires. +, low and high or some stupid park circuit included in the wiper switch.

So, I ask again: If you turn the wiper swich on and off for say a second or so, do you get a COMPLETE sweep.

 

[alec_t]

Can i increase the on time from 0.5 sec to 1 or 2 sec?

Yes. Increase R3 (presently 6.8k) to 12k or 27k for ~1 sec or 2 sec respectively.

 

[LouCi4er]

Thanks a lot Alec.That's what i did,almost.I connect the pin 4 and pin 5 with a resistor.With 30k it gave me 3 sec which is exactly the time needed by wipers to complete one cycle.Now its working perfect.Thanks again.

 

[LouCi4er]

Vapor lock in your case? The headlight problem was the bulb failed shorted and had a thermal breaker.

My question about your wiper is if the dash wiper switch is simply 3 wires. +, low and high or some stupid park circuit included in the wiper switch.

So, I ask again: If you turn the wiper swich on and off for say a second or so, do you get a COMPLETE sweep.

Park system is part of the switch,the switch has 5 wires.1 is the ground,2 is the first gear,3 is the second gear,4 is the parking and the 5 is the wiper squirters.+12v is directly from the key switch to the motor.If i open the switch for a sec and immidiatelly close it,the wiper will continue to swipping until they park,a complete sweep.

 

[KeepItSimpleStupid]

Thanks, so you just needed a bit more time to engage the switch.

The next step, would be just how to connect or operation.
One way would use a potentiometer with a snap switch, where when the switch is on, your full low speed.
Another would be a switch to say intermittant low, and full low and rate.

Glad it works.

So, I bet your engaging the relay for essentially 1.x sweeps, so you get a sweep from park and a full sweep?

 

[LouCi4er]

I gave constantly +12V to the circuit and give it ground from a switch.The first moment the circuit gets power,it performs 2 complete cycles and then park.After that,the circuit close the relay for 2 sec every x sec regarding the setting of the potentiometer,then the parking wire drive the wipers to the home position.It works like factory system.

Well,i am not sure how i'll addapt the whole system.There is an optional switch with 4 scales,close,intermittent,low,high but i think it is expensive.I was thinking to add a simple switch to just turn on and off the circuit for the intermittent.Another thought is to remove the high speed from the switch (i never use the high speed on the wipers)and use this contact for the intermittent.I am not sure yet.For the moment i have an other "problem".I need one more relay to make it work.I must cut the parking wire that goes to the normal close of the relay (i use the normal close for the parking) when i use the low speed.Otherwise the wipers has a hesitation to begin the cycle everytime they reach the parking.WTF,wipers are so copmlicated that is hard to believe.