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Landy Wiper Control

Sick of having 2 speeds for my windscreen wipers. Nothing a 555 timer can't fix!

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Landrover's (series 1 to 3, 90's and early defenders) are the definition of basic engineering. However the same is said for their mod cons!

Driving in the rain is not problem, but when the rain isn't that heavy, I find myself hitting the column stork intermittently it clear the windscreen as leaving the wipers on constantly is futile as its just getting in the way more than the spot of rain are!

Recently the switch that controls the screen wash jets stopped working, so saw an opportunity to improve my wiper system whilst I am trying to get a replacement wiper control system fitted.

This is intended to be a short project that I can do quickly on evenings and weekends

here things will go

Recently the switch that controls the screen wash jets stopped working, so saw an opportunity to improve my wiper system whilst I am trying to get a replacement wiper control system fitted.I fitted a new centre console on the dash to accommodate the new switches and fitted some existing accessories to it:

Finding stuff out

The existing wiper system is controlled by a stork on the steering column. There are 4 positions:

  • Centre - off
  • Momentary position which you push down on the stork, which allows one single wipe of the screen
  • Push up one position to engage a slow constant wiping motion
  • Push up again for a fast constant wiping motion

Though you can barely tell the difference between the first and second positions. The metal barrel at the end of the stork should have a plastic fitting over it, and shorts out the Green-Black wire to it, thus operating the pump in the screen wash bottle.

The switch is connected to the rest of the wiring loom with a connector:

Wire colour and switch functions where found to be:

Wire ColoursFunction
GRNWiper accessory power from fusebox
GRN to GRN-REDSingle (MOM position)
GRN to GRN-RED & GRN-BLUslow constant (1st Position)
GRN to GRN-REDFast constant (2nd Position)
GRN-BLK - BLK(Link From Ancil. Feed in - GRN)Screen wash switch
GRN-BRNStays at 12V whilst wiper is moving

The connector is a land-rover proproprietary one and is nicely moulded in rubber. In order to interface with this I have 2 options: Find an old switch and butcher it, which I am reluctant to do, even old spares are pricey. Or use some mating bullet crimps, which fit perfectly, and run some wire behind the dash from circuit the console to the connector.

Power must come from the GRN wire as it is fused and I don't want to start a fire!

The Circuit

The circuit is based on a 555 timer. I require it to vary the time between wipes, so the typical 555 astable circuit is the prefect for this application.

Rather than using a variable resistor, I decided to use a multipole switch and toggle between different resistor values. So say 3 different values for 3 different intervals and also another positon to allow the original constant function (S2-4 and Q2). J1 & J2 are there to suit the functionality of the automotive relay which will be connected to the output.

I chose a relay to drive output as its the simplest way when compared to using a BJT and MOSFET and not fully knowing the topology of the circuit being driven; Wiring diagrams are very vague and even if you understand it, you can't guarantee its right for your model.

The period of the 555 astable circuit is given by:


Where the space is time the output of the 555 timer is low, so Ideally I want this a fixed value as the time the relay is on for should be about 1 second-ish. This turns the output relay on by pulling the coil low. The mark time will be the time between these events, so by substituting in greater values of R1, should give longer duration between wipes.

How the circuit fits in

U1 is the circuit fitted inside an ABS box. S2 will select the interval between wipes. Wiper-Rot is an old double position rotatory switch with a push button function (which I already fitted to the centre console, mostly as a reminder to do this project!)

Switch S3 selects between the output of the 555 circuit and the fast constant wipe for RY1

RY1 being an automotive relay can handle quite a lot of switching current when compared to typical PCB mount relays and are easier to service so hence why that is there.

With Wiper-Rot closed and S3 in the 'up' position the timer circuit powered. When the output of the circuit goes high it will turn on RY1 for the time Tspace, which will be approx. 1 second allowing the wiper motor to start turning. After the 1 second interval and RY1 returns to the NC position, the motor wil continue to turn from the +12V recived on the GRN-BRN wire, until the wiper is parked.

With S3 in the 'Down' position, the wipers will be in constant fast mode and RY1 will...

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wiper wiring.PNG

Wiring Diagram / how it all goes together

Portable Network Graphics (PNG) - 60.09 kB - 11/06/2017 at 23:37

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Wiper interval-Transfer.pdf

Transfer of PCB, bottom layer as viewed from top

Adobe Portable Document Format - 9.07 kB - 08/03/2017 at 12:24

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Wiper interval-Sch.pdf

Schematic of circuit

Adobe Portable Document Format - 14.77 kB - 07/30/2017 at 22:19

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Wiper interval-Dwg.pdf

Drawing of overall board outline and component placement with dimensions

Adobe Portable Document Format - 11.83 kB - 07/30/2017 at 22:19

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  • 1 × Automotive relay socket
  • 1 × Automotive relay (SPCO/SPDT)
  • 1 × 130k Resistor, 0.25W, TH
  • 4 × 10k resistor, 0.25W, TH
  • 3 × 100uF Capacitor, 25V, TH

View all 18 components

  • Demonstration

    Tron900012/19/2017 at 16:06 0 comments

    As promised a video of it working. To follow will be a video describing how the circuit works.

    We've had a bit of crap weather here, and its performed precisely how I wanted it to!

  • It's in and working!

    Tron900011/06/2017 at 23:31 0 comments

    whilst hunting for a problem with My headlights I thought it would be a good opportunity to wire in the wiper interval box.

    After some swearing and a

    lot of fault finding, I manged to fit it and it works!

    I promise to get a video of it working soon.

  • Its in the Box

    Tron900010/06/2017 at 12:12 0 comments

    Getting back to it: I quickly tested my circuit with an actual automotive relay connected to it and it worked!

    I decided that it was the time to get this in a box. Drill a hole in the side and fitted a grommet, unsoldered all the wires off the switch and relay, passed them through the hole and resoldered all the connections with heatshrink:

    I glued the PCB to the lid of the box with some hot glue, which I don't know if it was a bad idea, but the alternative was Araldite, which would be more permanent. Then using a faston crimp terminal, removed the red plastic sleeving and inserted it into the pole terminal of the relay, making it change over configuration as required. 

    I could glue this contact in place as it doesn't have the tang to hold itself inside the relay holder like the other contacts, but its holding itself with its own retention well enough.

    It is now ready to be installed behind my centre console in the landrover. A job for another day.

  • Post Summer Update

    Tron900009/28/2017 at 08:35 0 comments

    Been on holiday. When I got back there was a huge amount to get done at work and home so not really had time to get this installed yet. Rest assured with impending winter weather, it will be installed!

  • PCB Assembled

    Tron900008/15/2017 at 21:37 0 comments

    I managed to drill and assemble the PCB and even got round to doing a quick test:

    a power on and jumping out so switch connections reviled all functions good, even the constant slow switch position. 

  • PCB #2 - A better outcome

    Tron900008/06/2017 at 21:10 0 comments

    So I decided to have another go at etching another PCB. I found some bare PCB without photo resist and thought try again, but change my technique a little bit.

    Firstly I rubbed up the copper first with some fine sand paper to 1) remove any oxide and contaminants and 2) hopefully roughen the surface to increase the chance of adhesion. I then taped down the transfer to the board using sticky tape - ideally you should use capton tape as I found when applying heat it shrinks, but so long as you don't leave it on so long it burns, its ok.

    I also decreased the time I applied heat from the iron. As you can see being a bit quicker allowed the toner to transfer and not the magazine ink, which seems to stick too.

    The transfer quality is much better than the last time, you can see the drill holes in the middle of the pads for a start! However it wasn't 100% perfect, and I still had to touch it up with a permanent marker. 

    After a FeCl bath and a rinse, here's how it came out:

    A massive improvement from the last time! I'm going to drill this and trim it to the final dimensions and get this soldered up!

  • First PCB Etch

    Tron900008/03/2017 at 12:22 0 comments

    I Etched my First PCB at home using the toner transfer on magazine paper method using the PCB transfer I made in EAGLE (See files I've added):

    NOT TO SCALE - DO NOT COPY, BOTTOM SIDE AS VIEWED FROM TOP

    I printed it off onto gloss magazine paper, cleaned the surface of the PCB, hooked up a heated pad to a  power supply to warm the ferric cholride and aid to speed up the etching process...

    ...then applied the transfer to the PCB using a clothes Iron with a sheet of foil between the paper and iron surface, Iron was cranked to highest setting and pressed down for about 5mins and after a bath in water, managed to peel off the magazine paper:

    Some touch-up was required with the permanent fine marker and then into the etch bath. Here's how it came out...

    Hmmm....not the best really, would work if i did a little fettling. I think the issue is I am leaving the iron on for too long and the toner is bringing the paper with it and also bleeding. 

    Unfortunately this was the only piece of bare copper clad I had, the others have photo-sensitive resists on them, If i can get hold of some transparency and leave it out on a sunny day then I could get the same result. I have some more bare copper coming soon.

    I'm going to make another attempt either using the photo-resistive stuff or the bare clad when it arrives.

  • Schematic and board layout complete

    Tron900007/30/2017 at 22:23 0 comments

    So I've done a quick schematic and done a board layout, which I have uploaded to my files for this project (see above).

    I'll upload the trace transfer once I've verified it works and comes out OK from the etching process.

  • Some Purchases...

    Tron900007/28/2017 at 21:16 0 comments

    Today I went on Amazon and bought a pack of 10 single-sided copper clad boards, some ferric chloride and a toner cartridge for a laser printer I found in a recnet dumpster dive that worked.

    My plan is to try out the toner transfer method of making my own PCB's and hope to make one for this project.

    Time to dust free-eagle and get the PCB designed!

  • Additions to my interval circuit

    Tron900007/26/2017 at 20:19 0 comments

    Had a quick tinker with this project last night.

    With the new update for the wiring schematic meant that the output of my Interval circuit (see above).

    The relay I'm controlling requires it to be driven by 12V instead of being pulled down to 0V.

    Considering that the output of the timer is low for <1 second and high for the set interval, I need a PNP or P-channel MOSFET to drive the relay from the 555 timer output.

    The chosen device to do this: 2n3906 - cheap, readily available, and up to the job.

    After bread-boarding up the circuit, I came up with this schematic:

    It works well but there is a strange anomaly where upon first power up and the reset circuit (consisting of R7, R8, C3 & C4) forces the output low, there was a delay between the output of the 555 going low and the test relay I was using energising. After that it worked as expected.

    As you can see I also connected one of the positions of the rotary switch (S2) directly to pins 2 & 6 of the 555 timer. This is instead of bypassing the 555 altogether and connecting power directly to the relay. The reason for this is that according to the 555 datasheet:

    So with 12V at these pins, both conditions are satisfied and the output will be low constantly. However this will need testing first.

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