Author Topic: Another question for the electrical guys. (Read 2013 times)

Jamieg285 · « **on:** November 01, 2007, 11:38:43 am »

I'm currently investigating electric fan controllers. The one I am looking at uses Pulse Width Modulation to move the fans at varying speeds between 50-100%.

I don't fully understand how it works, but need to know if the feed to the fans would also be suitable to run an LED, or a relay?

55starchief · « **Reply #1 on:** November 01, 2007, 11:41:59 am »

PWM is basicaly very gast switching of transistors

No you wouldnt be able to use the same feed from the controler

55starchief · « **Reply #2 on:** November 01, 2007, 11:57:23 am »

Why bother with a fan controler seems an added expense, never used one on anything i have built usualy just use a ford sender unit

Jamieg285 · « **Reply #3 on:** November 01, 2007, 11:59:04 am »

I wasn't aware of any other way of doing it. What does the Ford sender do?

55starchief · « **Reply #4 on:** November 01, 2007, 12:04:55 pm »

It just switches the fan of and on when the temp is equal to that of the sender unit, form memory its 80*c and of at 90*c. All you need is a piece of tube wich you install in the water pipe and a oouple fo wires to hook up to the relay that switches the fan

http://www.westfield-sportscars.co.uk/shop/product.asp?numRecordPosition=14&P_ID=218&strPageHistory=cat&strKeywords=&SearchFor=&PT_ID=75

http://www.westfield-sportscars.co.uk/shop/product.asp?numRecordPosition=15&P_ID=336&strPageHistory=cat&strKeywords=&SearchFor=&PT_ID=75

Just remember to ask them for the plug connector

Titsy · « **Reply #5 on:** November 01, 2007, 12:25:38 pm »

what he said...

55starchief · « **Reply #6 on:** November 01, 2007, 12:29:23 pm »

Quoting: Titsy

what he said..

wow i remebered something from one of geoffs lectures

Jamieg285 · « **Reply #7 on:** November 01, 2007, 12:30:21 pm »

OK, I'll guess a re-think is in order.

F Body · « **Reply #8 on:** November 01, 2007, 12:40:07 pm »

The only electric fan I've fitted was a Kenlow and that had an adjustable thermostat which coupled to the sender

Jamieg285 · « **Reply #9 on:** November 02, 2007, 03:10:58 pm »

Another question on fans. Do you get the same AMP reading on the negative side of the fan as on the positive?

Titsy · « **Reply #10 on:** November 02, 2007, 11:23:03 pm »

Current is measured serially... You meter forms part of the circuit, and what ever point in the circuit you put the meter it will measure the same... Think of electricity and wires in terms of water and pipes... voltage is the presure of the water, and current is the rate that water flows throught the system...

art b · « **Reply #11 on:** November 02, 2007, 11:40:51 pm »

electricity [a charge] flows from one point to another,
If there is a [pd] potential diference between two pointe ie; +and -
The charge will always flow until the force acting on it is reduced to a minimum, or until the voltage becomes the same ie a flat battery both + and - are equal,

Jamieg285 · « **Reply #12 on:** November 03, 2007, 08:29:54 am »

Fair do's.

One more quick question - for now

In a high amp application, i.e. 50A+, rather than using a HD 70A relay, could you run 2x40A relays, wired in parallel to do the same job?

Titsy · « **Reply #13 on:** November 03, 2007, 08:37:36 am »

That should work fine... the instantanious current ratings are a bit higher than the continuous current ratings, so even with one switching fractionaly quicker than an other it should be fine...

55starchief · « **Reply #14 on:** November 03, 2007, 12:16:48 pm »

Why run 2 relays when you could simply run one large one, the cost must be about the same and if one 40A fails you have a problem with over current. The point of running two relays would be to run a pair of 70A units

Jamieg285 · « **Reply #15 on:** November 03, 2007, 08:06:46 pm »

The reason is that ideally I want to run a SPDT, but I've not found any higher than 30A yet.

Jamieg285 · « **Reply #16 on:** November 05, 2007, 08:34:55 am »

Also, 2x30A SPDTs are cheaper than 1 70A (+ if I had to use the 70A, I'd still need 2)

55starchief · « **Reply #17 on:** November 05, 2007, 09:57:32 am »

Quoting: Jamieg285

Also, 2x30A SPDTs are cheaper than 1 70A (+ if I had to use the 70A, I'd still need 2)

but your load is 20A higher than that so you need the 70A anyway

Jamieg285 · « **Reply #18 on:** November 05, 2007, 10:19:08 am »

The fan has a high and low input - the draw could be up to 50A.

If I use 2 x SPDT(30A) in parallel, I only need 2 relays to switch from Low to High. If I have to use 70A relays, I need 1 for each side, + another 30A(or lower) to control them.

In either case, there will be a manual override option, in case of any component failure.