Heated Screens

[toomanysabres]

If you can find out what wattage the elements are designed to safely dissipate then its simple to work out which configuration to wire them in.

That's the engineer in us agreeing. BUT get Ohms law on the go from my earlier post.
Series connection 8A 12V = 96W = nicely warm methinks I would go with that.
Now work out half the resistance and 12V on each half and you have 192W x 2 = electric fire
If nothing else I don't want it to fry the sat nag rubber sucker.

[toomanysabres]

Right, phoned up and spoke to Dan (Ricky's son).
Its not completely clear cut.
The majority of their windscreens go into competition cars. Especially special stage rally cars. Where they need clearing asap. The heater will likely only be on for a short time and the navigator will switch it off after only a minute or so. So full power to both sections.

With it getting 'quite hot' (my words) there is likely to be a temporary 'wavy distortion' (their words) visible through the window. So for a road car and possibly ending up being on for some length of time I would recommend connecting up a two section window in series. You could also fit a delayed off relay.

Full power to an SE5/Coupe half section will draw about 16A so the twin relay & fuse diagram on their web site should be followed I think.

Just unwrapped my Sabre 4 window and it only has one element. I'm going to leave my Coupe in series.

Next time I think about it I could set the rear demist on the BMW and see how long its own off timer runs for.

Hope that helps, but you need to decide for yourself how you want to run it.

[toomanysabres]

I have had a reply email from Dan as I copied it to him, so reproduced here FYI.

That is fine, we just don’t want people thinking that any distortion in the glass is a fault in the screen! All that is.. is the screen getting too much power and therefore getting too hot – I would assume most of these chaps will be using them for a nice restored road cars and shows so series is how they should be wiring them – same the rear screens we do as well.

Cheers
Dan

[windy]

If you are really clever you could rig up a high/low switch, for those frosty mornings. Needs a bit of thought though

[philhoward]

A DPDT relay or a pair of Single Pole changeover relays?

[toomanysabres]

Yeah If you have a rear window also with twin elements you could have more than one outside thermometers to decide what is best for the morning rush hour (giving some more time in bed) and a timer to avoid a flat battery, then you would need the following parts
http://www.amazon.com/Invincible-Marine ... 3398801_12
and

and

or

Then a nice tidy housing like this
http://www.google.co.uk/imgres?imgurl=h ... MwgpKAkwCQ

[philhoward]

I can imagine AJL has already written a Raspberry Pi for it...

[AJL Electronics]

Arduino is better for that and there are some nice temperature and humidity sensors for it too. DHT11 or something like that. You could have auto operation I suppose!

[gordini5]

Just unwrapped my Sabre 4 window and it only has one element. I'm going to leave my Coupe in series.

Next time I think about it I could set the rear demist on the BMW and see how long its own off timer runs for.

Hope that helps, but you need to decide for yourself how you want to run it.

I don't use it much and assumed my Ford windscreen was temperature sensitive but just tested it and it was exactly 5 mins either from cold or warm before it shut off. That helps explain why on warmer days the distortion can become quite distracting and maybe occasional over-heating is the reason why at least a half dozen elements/wires are now broken.

Is the thought here then to go for series connection on a 5a if we know that works okay on a coupe?

[philhoward]

I would say that what works for a Coupe will work for a 5a given it's the same screen - series operation should still clear it in a minute or two, weather dependant of course.

If you wanted to be clever, you could sort out a "boost" button for a minute. Just had a quick look on ebay (for ease) and a plethora of timer relay units which would give you (with a couple of other relays) automatic parallel operation for about a minute, then on series operation for (say) 5 minutes.

[toomanysabres]

I don't use it much and assumed my Ford windscreen was temperature sensitive but just tested it and it was exactly 5 mins either from cold or warm before it shut off. That helps explain why on warmer days the distortion can become quite distracting and maybe occasional over-heating is the reason why at least a half dozen elements/wires are now broken.

Is the thought here then to go for series connection on a 5a if we know that works okay on a coupe?

I would do it series and I'm a bit gobsmacked that Ford would have the same overheat issue that was referred to about ours.

[philhoward]

I wouldn't (be surprised) - fixed timer, no thermostatic control? Cheap - which is how Ford like it..

[Roger Pennington]

I vaguely recall my brother mentioning something about occasional slight distortion when I was a passenger in his Focus (the closest I've ever come to such luxuries as a heated screen!). Are other cars temp as well as time controlled?

[philhoward]

I know the heated mirrors on my company car are (PWM)..sadly it doesn't have a heated screen to check!

[toomanysabres]

My 'luxury' BMW has heated mirrors but doesn't even have such a windscreen although there are some wires only just where the wipers park and even that didn't stop a blade welding to the glass and pulling back a couple of inches once. The top of the arm carved the glass damn it.