Pull-up resistor

[Bob O 8]

I have never need to use a pull-up resistor before but now I am told I need one. The manufacture recommends a 10kW pull-up resistor. I am wiring into a ML1100. I used the equation below to calculate the resistor size and came up with .0576 Ohms. P=V^2/R V=24VDC P=10 kW R=.0576 Ohms Is this correct? Thanks, Bob

[mvandyke 0]

I think the manufacturer means to use a 10Kohm resister.

[Bob O 8]

They have 10 kW listed and the sensor can be powered by 5-24 VDC so that is why I was calculating an R value.

[ianbuckley 0]

Your equations are fine, but you don't need a 10kW resistor to wire into a ML1100. I am sure they meant 10KOhm resistor. A quarter or half Watt resistor should be fine. Whatever they have at the local Radio Shack or similar. A 10kW 0.0576 Ohm resistor would pull 416 Amps at 24VDC!

[gravitar 3]

We use components on our welders of the resistance and power-handling capablilty you mention . We call them shunt cables

[Bob O 8]

The manual is incorrect so all is good now.

[BobLfoot 301]

In defense of the manual the true story goes something like this. in the PLC design lab the engineer tells his assistant we need a 10 KiloOhm resistor for pullup. The overworked and busy assistant or his engineer puts 10 K ? in their sloppy handwriting. This then winds up on the desk of an even more overworked technical writer who thru a string of eplicatives wonders where the tech or engineer learned to write and types it 10KW. Since KW is a valid modifier for a resistor months later when proofing the manual no one catches it. And wallah you the end user must catch the error.

[Bob O 8]

Please don’t get me wrong this wasn’t a big deal.

[Mickey 71]

http://www.kpsec.freeuk.com/faq.htm From the above web site: A project on another website lists a 10kW resistor! What does it mean? It almost certainly means a 10k resistor. This is a common error which occurs when the web page specifies a Greek font. If this font is not available on your computer you see the character in your standard font and it happens to be W which is the symbol for watt, the unit of power! I avoid the problem on this website by using a small image for . In a few projects a low value resistor with a high power rating is required but the power will be something smaller like 5W, never 10kW which is more powerful than an electric heater!

[BobLfoot 301]

good point mikey I never even considered that the greek font with omega symbol might have been loaded on one PC and not another.