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windscreen wiper motors


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Glen
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Joined: 16 Jun 2004
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windscreen wiper motors

lots of questions here -

i just had a bit of a look at some of the windscreen wiper motors in that rexs robot challenge magazing article thing and im wondering about how the WW motors actually work.

mainly im wondering what purpose those two choke coils have that are inside the motor case itself on a little circuit board. i have a bit of a suspicion that they have something to do with the autopark feature or how the motor runs in "slow" mode but im not really sure.

following on from that im wondering how the slow mode actually works.. i havent tested the current on it to see if it goes up or down in slow mode so im not 100% sure that works either. im thinking that those coils act as resistors of some kind..

the big thing that has got me dumbfounded is how the auto park feature works.. (the auto park feature is where the windscreen wipers return to their down position even when the switch is off) i know that the 2 spare pins are there for it, but am not sure as to HOW it actually works. im guessing that there is two seperate circuits in the car or something and a limit switch on the wiper arm that lets this all happen.

any clarification would be great as ive found only 1 decent article on google.
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Post Sat Jan 22, 2005 9:13 pm 
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Knightrous
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Joined: 15 Jun 2004
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You will actually find the ww motor has 3 brushes in it. two in the normal 180 degree oppisite position and the other is 120 offset from one of them. if you run the low speed, your using the two brushes directly opposite each other. If your run the high mode, your using the brush that is offset to the others. This changes the timing and speeds the motor up Smile

Damn, I just realised how long ago it was when we were timing ww motor for Vertex, nearly 3 years ago! Shocked I'm starting to feel old Razz

EDIT: Added diagram here: http://www.robowars.org/forum/album_pic.php?pic_id=575
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Last edited by Knightrous on Sat Jan 22, 2005 9:35 pm; edited 1 time in total

Post Sat Jan 22, 2005 9:26 pm 
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timmeh
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Joined: 20 Jul 2004
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Location: Victoria


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Found this on thuis web page http://www.geocities.com/sprite-midget/wipers.htm

Flicking the toggle switch to the first position (slow operation), power is applied to the relay, closing the contact and supplying power to pin 5 on the wiper motor (via pin 87 and 30 on the relay). The Auto Park connection on the Wiper Motor (pin 2) is not connected to anything while the relay is energised.

Flicking the toggle switch to the second position (fast operation), power is supplied directly to pin 3 on the Wiper Motor. At this point you might expect the relay to turn off, but in fact the relay remains turned on by current leaking back out of pin 5 (slow) of the wiper motor (via pin 30 and 87 of the relay). The Auto Park connection on the Wiper Motor (pin 2) is not connected to anything while the relay remains energised.

Flcking the switch to off, causes the relay to turn off, this connects pin 2 of the Wiper Motor to pin 5 of the Wiper Motor (via pin 87a and 30 of the relay). What I think happens here is that power is connected to pin 4 of the Wiper Motor, this must be internally connected to pin 2 via a switch, which allows us to continue to supply power to the slow pin 5 of the motor until it reaches the park position when pin 2 turns itself off.
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Post Sat Jan 22, 2005 9:30 pm 
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Glen
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yeah i knew about that website tim, that was the one good one i was talking about Smile


quote:
until it reaches the park position


thats what im curious about, Where is the park posititon, is it a microswitch on the wiper arm or what.

thanks for that brush diagram too. im wondering if you could reposition that brush at 90 degrees from the other 2 and try get more power out of it Very Happy
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Post Sat Jan 22, 2005 10:59 pm 
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Totaly_Recycled
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The park switch on most ww motors is two copper tracks on the rear of the plastic worm gear these have contact brushes to the conector plug and motor the copper tracks have a gap that the brushes slide onto the insulated gear and the motor stops in that position .

Post Sat Jan 22, 2005 11:14 pm 
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DavidM



Joined: 07 Jul 2004
Posts: 41
Location: Victoria, Australia, Earth, Milky Way Galaxy


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The coils and capacitors inside the WWM are for EMI (radio interference) suppression. This so that you can listen to the radio and not just listen to the sound of hash from the brushes inside the WWM. I still find extra suppression is required when using microcontrollers or R/C.
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Post Mon Feb 07, 2005 6:19 pm 
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Shaunington III



Joined: 18 Jan 2006
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If you plan on useing windscreen wiper motors, use old x3, just make sure they have a long enough shaft, i made that mistake... Razz

Post Sat Jan 21, 2006 3:25 pm 
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