Clean It Up
UK Window Cleaning Forum => Window Cleaning Forum => Topic started by: Spruce on March 26, 2014, 08:34:29 am
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Hi Ian,
A question I have wanted to ask for a while with regard to polarity.
We all know that taking a battery out of the van every couple of days to charge it can increase the chances of an operator/owner getting the battery terminals mixed up and cooking his controller. Some of us (including me) suffer with this more than others do. (I do to such an extent that I have a Torberry Anderson plug on the end of my charger wired in to the system on each van so it's impossible for me to get it wrong.)
Is there some way of fitting an inline 10 amp diode before the controller to save the controller if polarity is accidentally changed?
Thanks.
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I have an inline fuse inbetween battery and controller if thats what you mean?
The fuse blew when i accidentally wired to the wrong terminal but controller was fine...
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We do the same as don k, an additional inline fuse to each controller
Darran
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This seems reasonably straight forwards:
http://www.instructables.com/id/Reverse-polarity-protection-for-your-circuit-with/
When I had a flow controller I used a 12V relay to switch any voltage up to 240V. If it was connected the wrong way round, the relay switch wouldn't work.
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This seems reasonably straight forwards:
http://www.instructables.com/id/Reverse-polarity-protection-for-your-circuit-with/
When I had a flow controller I used a 12V relay to switch any voltage up to 240V. If it was connected the wrong way round, the relay switch wouldn't work.
Thanks Rosskesava,
I'm not into electronics, so am having a hard time trying to get my head around what is probably a rather simple component. I need to study this and try to understand it.
I know a diode will only let current through one way, but I didn't know that the voltage drop could be a high as 0.7v. This voltage drop is probably the reason why manufacturers don't use diodes then.
Thanks again
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Spruce, if you look at diagram 3, the voltage loss is almost zero and the component is rated for 12V up to 17 amps.
http://www.digikey.com/product-detail/en/SI4838DY-T1-E3/SI4838DY-T1-E3TR-ND/1656477
You could probably buy that from Maplins, Ebay or somewhere similar.
Maybe try somewhere like gumtree for someone who could wire it in for you.
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Thank you Spruce and Rosskesava
Good points raised by you both. I will try to cover them as best I can
To Answer Spruce,s point all our controllers for some time have had a reverse polarity diode fitted on to the PCB. It is placed so we can protect the pump driver, majority of the circuits and processor from reverse polarity.
We also recommend and supply the appropriate fuse and holder to be fitted on the Positive lead (red) between the battery and control.
As Don points out fitting the fuse can help protect the controller and diode in the event of reverse polarity. For this reason on the bottom of all the installation guides we state.
1. Make sure correct fuse is fitted inline. Failure to do so will result in damage to the unit.
2. Observe correct battery polarity. Failure to do so will result in damage to the unit.
As Spruce pointed out yesterday in another post the fuse should be fitted as close to the battery as possible to protect the wiring after the fuse. The most likely cause of a power spike or short is from the power source (battery). Hence the less distance the short can travel between source and fuse the better.
It is also for this reason we do not pre fit the fuse but supply a kit.
The following link gives a little more detail http://www.springltd.co/node/136
To cover the suggestion by Rosskesava fitting a lager diode to offer higher levels of protection is an option. However larger diode would generate more heat and make the unit less efficient. To counter this would require us to fit larger heat syncs, FETS together with upgrading the copper tracks on the PCB. The result would be a larger unit which would also increase the cost of the unit.
The Controls are supplied with 1mm Tri cable rated to 18amps. The control itself is rated to 10 amps. We also fit an over current protection circuit on to the PCB so if the unit see,s a sudden spike in current it shuts down the pump to protect itself.
In effect then we provide three levels of protection
1. Reverse polarity diode
2. Supply and recommendation to fit a fuse
3. Over current protection
It is a discussion I have with my MD and Tech director from time to time. When we look at numbers of controls returned due to blown reverse polarity diode it is a tiny fraction of what we produce. We look at a balance between trying to provide as much protection as we can while producing an efficient control at reasonable cost.
When compared to the 1000,s of units we produce we might see 50 or 60 a year. Because the diode is fitted we can repair the control, which we do for a small charge. If we can not be sure what has caused the failure and the control is within its warranty period we give the user the benefit of doubt and repair under the warranty.
From what we see the issue of reverse polarity damage to controls is diminishing this is in large part thanks to greater awareness raised by cleaners themselves.
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Thank you Ian for the time and effort you put into this very detailed reply.
It also goes to show how products are being continually updated and I don't always keep abreast with those updates/improvements.
When Rosskesava put up the link that showed the possible voltage drop over the circuit using a diode, I immediately thought that this was a good reason for not fitting one in our controllers.
This has been a question in the back of my mind for years, but haven't asked it. It was a recent thread that kicked off my thought processes again.
It's good to know that the products you sell cover as many things as possible
Cheers for this update.