car electric window motor

[haris_216]

Hi there all
I am here to explain you my problem and, hopefully, find a solution.
In my car there was the usual (for last century ) hand cranked windows. Some ten years ago I put an aftermarket spal system which uses the car's mechanism by attaching a motor to it. As a universal solution was ok up to recently when the drivers side failed. Not the motor itself but actually the "gearbox".
Since the window mechanism started to get a bit loose due to age I thought to go for a motorized mechanism and not the "hybrid" I had up to now.
The problem is that given the age of the car (Ibiza mk1) a pair of electric mechanisms cost almost as much as the car (if not more ).
I did find new valeo motorized mechanism at a suprisingly low price only to find out that there was a reason for that low price. The unit doesn't have the thermal motor protection that cuts out the motor when reaching the end of the travel or an obstacle (head or hand). It will keep pushing till you let it go (or till blow the fuse).
My question is this: Is there any possible (affordable) way that this short of cut-off protection can be added to the motor? I wouldn't go for the option of putting some sort of sensor at the end of the window travel because it would solve the up'n'down problem but not the possibility of an accident (in case something goes in the window's path)

 

[alec_t]

Yes. A circuit which senses the motor current and either limits it to a safe level or cuts it off completely when it exceeds some limit would protect the motor (and anyone blocking the window movement ). The trick would be to find the optimum current limit and to provide a timed delay to enable the motor to start up, bearing in mind that at start-up, or when the motor stalls, the current drawn is several times the normal running current.

 

[haris_216]

Thanks a lot mate for your response.
To be honest I thought that it would probably need some tailored (to the specific motor) solution.
Do you (or anyone else) think that you can guide me towards a general circuit solution or even the right googling terminology? I do have some very small amateur experience with electronic circuits but given than english isn't my mother tongue am not sure even if my searches at google are at the right direction
Is it possible that I use a general circuit for sensing and limiting current and perhaps "play" a bit with different values in components in a "try and error" sort of experementing?
Any other ideas?

 

[MaxHeadRoom78]

Is there any auto wreckers close by? You could get the whole unit for a few $$'s., electronic breaker and all.
Max.

 

[haris_216]

That was my first choice.
Unfortunately, although my car was pretty popular in its time, that's not the case anymore.
Also some measures taken by the goverment for renewing the car fleet's age in Greece many years ago, had the result that most of the cars of the era went to the press. Those left now are, in most cases, the 5 door models (mine is the 3 door) as the model has enough space inside and is adapted mostly by technicians (plumbers, wall painters, etc) resulting in me being able to sourse through the scrappers most of the things I need occasionally but not the specific mechanisms, since there is differense between the 5 and 3 doors models.

 

[KeepItSimpleStupid]

Here **broken link removed** is a anti-pinch reference design.

They need to be a little smarter than "stop" when an overload is sensed. The motor needs to back-up a bit.

If this was a spoiler, then returning to full up or full down would make sense.

Two cars have auto-down, but I don;t know about obstacle protection. I do know that one has a thermal that did open one day when the car was sitting.

A PTC thermister or "Polyfuse" is generally designed to protect from motor overloads. ICE and meachanism jams would come to mind.

Pocket door opening devices can be complicated too. Probably more complicated than windows.

So, it all starts with a normalized profile of voltage and current by position. Battery voltage could have an effect

A human arm stuck in a window and the motor stopping would not work. The motor should stop and reverse an inch or so.

 

[haris_216]

Thanks a lot for your suggestion. Already downloaded the pdf and started reading.
It does seem very interesting although a "bit" out of my "comfort zone" of my small experience I have with electronics and the the no experience in the programming field.
But even before getting to that am already puzzled as to how to include the hall sensor and magnet to the rather restricting space of the all metal motor/gearbox assembly. I didn't think I was gonna need something in that area and all the "work" would be done in the power feed of the motor

 

[rjenkinsgb]

It may work with nothing more than a "polyswitch" type solid state fuse.

They switch to high resistance when their rated current is exceeded long enough (as they get hot) and then reset themselves when the load is disconnected / switched off & they cool again.

You need to measure the motor current in normal operation and when it stalls, then pick a suitably rated device.
They are available in current ratings from fractions of an amp to over 25A.

Some examples, similar things are available from many electronics suppliers:

Resettable Fuses | SMD & Wire Ended Fuses | RS

Resettable surface mount fuses are a reusable type of circuit protection device that are able to be mounted onto printed circuit boards.

uk.rs-online.com

 

[haris_216]

Another option that I never thought (actually heard) off.
Just a couple of questions that popped out of my head, in case anybody knows.
Those "resettable" fuses are for resetting continously? I mean using the motor up n down normally it will trip the fuse in both directions every time it reaches the end of the travel. Can they cope with this kind of use or they are for a limited "incidents"?
And how long it will take for it to re-arm? A second or so after cutting power or far more than that?

 

[alec_t]

I would be concerned that a polyswitch wouldn't react quickly enough, or wouldn't be sensitive enough to modest overload current, to provide an anti-pinch function.

 

[KeepItSimpleStupid]

Reading the TI brief, down doesn't require pinch detection.

Under high loads, the brushes tend to get damaged. Had that happen with a heater blower motor. Temperature and gravity causes the blower to hit killing the brushes over time.

 

[rjenkinsgb]

Can they cope with this kind of use or they are for a limited "incidents"?
And how long it will take for it to re-arm? A second or so after cutting power or far more than that?

They should work pretty much forever. On the smaller ones we use, the reset time is very short, a second or two.

If you get the correct rated type so it's not quite at the trip current under normal load, it should react fairly rapidly to a stall - far faster than the motor itself will overheat.

Re. the "pinch protection" that keeps being mentioned - if the previous system only stopped when obstructed, I can't see it being an essential requirement for the replacement. It would be different if the older one had that.

I suspect it's more a requirement for "one touch" window controls that continue to move after the button is released.

A polyswitch is not perfect, but a more advanced system requires limit switches or digital position tracking, as well as current monitoring..

 

[haris_216]

Hi there
Thank you all for your interest and participation. You sure did gave me ideas and approaches.

 

[haris_216]

Re. the "pinch protection" that keeps being mentioned - if the previous system only stopped when obstructed, I can't see it being an essential requirement for the replacement. It would be different if the older one had that.
I suspect it's more a requirement for "one touch" window controls that continue to move after the button is released.
A polyswitch is not perfect, but a more advanced system requires limit switches or digital position tracking, as well as current monitoring..

I do agree, by those said here that this "polyswitch" is my best option comparing function vs simplicity. I will try and see how it goes.
Of course I don't have "problem" if more ideas/options keep pouring in

Question: Given that the window motors have two wires with polarity changing depending if they go up or down, do those polyswitches have a polarity preference or can be conneted either way?

You are right regarding the "pinch protection". More needed in the "one touch" mode that I don't have at the moment. I have in mind of doing it but, altough I do have the needed relays, I haven't tried it yet.
And speaking of "one touch", I have a few from Ford (Mondeo perhaps) as i was planning to do the "one touch" even with my previous setup (the spal electric motors).
They are these:

Although I have seen those relays been used in "one touch" retrofitting to other cars, I haven't found yet the correct pin-out. There are models that have 4 wires and models, like the one shown which I have, that have 5 wires.
I have looked in various places (even ford forums) but with no clear answer as to what each wire represent or possibly a connection diagram.
Any ideas?

 

[haris_216]

Hoping that am not becoming too much of a burden to all of you, I have one more question regarding those polyswitches.
I have been done quite some reading on them since yesterday and there is a point that puzzles me.
They all have a "holding current" and "tripping current" parameters which appear to be one (almost) twice the value of the other. Of course the decision has to do with the specific motor and surely I am gonna do a bit of bench testing of my motor.
I do wonder though how those values are associated with the fuse that's already in the power feed of the system (20A)? Tripping value has to be definitely below in-line fuse value, right? Is there any need for this fuse to be removed from the circuit? (my guesses are not but thought to ask anyway)

 

[rjenkinsgb]

Polyswitches & other equivalents are not polarity sensitive.

The current ratings are totally dependant on what current the motor actually needs to operate, which is hopefully rather less than the 20A fuse. That must stay in line to protect from possible cable damage/shorts.

As it happens I do have the full electrical diagrams for a Mondeo (I drive one)..
When I have a bit more time I'll see if I can look up the window system wiring.

 

[KeepItSimpleStupid]

The fuse is for short-circuit protection, the poly-switch for overload protection. Two different functions. Generally, you protect the wiring first or you have the wiring fry in a protective place. A fuseable link is one such example.

The polyswich should be mounted to or very close to the motor. It will be affected by ambient temperature. That's why my window would not work on a very hot day. Temp > 100F.

From reading, the down direction does not require pinch protection.

 

[haris_216]

Polyswitches & other equivalents are not polarity sensitive.

The current ratings are totally dependant on what current the motor actually needs to operate, which is hopefully rather less than the 20A fuse. That must stay in line to protect from possible cable damage/shorts.

As it happens I do have the full electrical diagrams for a Mondeo (I drive one)..
When I have a bit more time I'll see if I can look up the window system wiring.

Thanks a lot mate. I'll be looking forward for diagrams when it is handy for you

 

[haris_216]

The fuse is for short-circuit protection, the poly-switch for overload protection. Two different functions. Generally, you protect the wiring first or you have the wiring fry in a protective place. A fuseable link is one such example.

The polyswich should be mounted to or very close to the motor. It will be affected by ambient temperature. That's why my window would not work on a very hot day. Temp > 100F.

From reading, the down direction does not require pinch protection.

Thanks for your comments.
I think even the "down" needs protection not so much as anti-pinch but rather to protect from the momentary motor stress when reaching end of travel.
Thanks for mentioning ambient temperature. Didn't think at all of it and given that I am in Greece I guess it would surely affect the function (tripping or even re-arming) during summer.

 

[shortbus=]

I think even the "down" needs protection not so much as anti-pinch but rather to protect from the momentary motor stress when reaching end of travel.

That is taken care of by the 'poly-switch'. The same way the top position is done. On GM windows the poly-switch is in the motor housing.