Wiper Motor Control

[fireflybuzzbuzz]

I am looking to add a delay to the windscreen wiper system on my '73 volkswagen beetle, as currently they are either on or off.

The wiper system currently latches untill the blades have returned to their parked position, so the way i thought of adding the delay was to simply generate a 1 second pulse at set intervals.

This being done using 3, 555 astable timers set to different pulse intervals with a rotary switch to select between them. (see attached image)

Delay Circuit 1 = 10 sec off, 1 sec on
Delay Circuit 2 = 5 sec off, 1 sec on
Delay Circuit 3 = 2 sec off, 1 sec on
Bypass Circuit = Wipers constantly on


The problem with this plan is that i have very little experience with electronics and no idea what capacitance and resistance values i should use. If you could help me choose what values i need, and more importantly show me how you selected them, i would be very greatfull.


- Buzz

 

[Reloadron]

Actually what you want can be done using a single 555 timer rather than 3 and you can have a delay adjustable between 1 and 20 seconds all variable. This link shows one example but there are plenty. Understand you are new to all this. Some of what you are looking for will also be determined as to how you interface the circuit to the wiper motor circuit.

Welcome to the forums.

Ron

 

[fireflybuzzbuzz]

Thank you for the help, however i dont belive that circuit would work as i am unable to seperate the motor and park switch because they are within a sealed unit.

Additionally, at the risk of sounding ungreatfull, i would prefer to build the circuit that i have designed as a matter of pride. the main purpose for this project being to see what i could achive by myself.

So if you could help me to calculate what capacitance and resistance i need i would be very greatfull, and thank you again for being so welcoming to a newbie.

- Buzz

 

[audioguru]

Wow! A '73 bug! Are you in Mexico?

I learned to drive on a '67 bug.

 

[fireflybuzzbuzz]

No lol, i'm acctually from the UK. Bought the car just after i passed my test, been welding back together ever since

 

[crutschow]

I put an all solid-state wiper delay way back when on my '63 GTO. I used a unijunction transistor to generate the delay (variable with a pot) which triggered an SCR to turn on the wiper. As soon as the wiper park-switch closed, it stopped the current through the SCR, resetting if for the next cycle, as the wiper completed its single cycle.

 

[fireflybuzzbuzz]

Yet again, the problem with the fact the wiper system is sealed occurs. The park switch is within the motor housing itself, not to mention almost impossible to get to (took me best part of 2 hours to remove it last service)

**broken link removed**

 

[crutschow]

The fact that the wiper motor is sealed is not necessarily a problem. The delay circuit I built was connected in series with the dash switch and did not require direct access to the park switch. When the park switch closed it bypassed the dash switch, which removed the power to the circuit and caused it to reset.

So if would help if you could show exactly how the wiper motor and dash switch are presently wired.

It's commendable that you want to build your own circuit, but good design means modifying the design if there's a simpler approach. Many can design a complex circuit to do a job, but the best design is the simplest.

Here's a reference to calculate the values for a 555 astable oscillator.

 

[Reloadron]

Thank you for the help, however i dont belive that circuit would work as i am unable to seperate the motor and park switch because they are within a sealed unit.

Additionally, at the risk of sounding ungreatfull, i would prefer to build the circuit that i have designed as a matter of pride. the main purpose for this project being to see what i could achive by myself.

So if you could help me to calculate what capacitance and resistance i need i would be very greatfull, and thank you again for being so welcoming to a newbie.

- Buzz

OK, you can roll your own and use three 555 timers as in your drawing. First you should likely get acquainted with the 555 timer and how it works specific to your application. **broken link removed** as well as other like it describe the chips operation and how component values are derived. There are also as mentioned countless 555 timer calculators out there online including one developed by the forums own Eric Gibbs.

I suggest you find a circuit like the one I linked to using a single chip and use that as your foundation with a variable resistor. Play around with the circuit and adjust the pot for assorted delays like you want to use. At each setting you want remove the pot and measure the resistance and note it. Then build your individual circuits as that is the way you want to go. Use the resistor values you noted in fixed resistors or as close as you can get. That or build three redundant circuits using pots (variable resistors) and set them for your delays you want.

Then configure the output(s) to drive your wiper scheme.

Ron