Light Bulb Inplace Of Power Resistors

[Khalid]

i have fet3-dynamo circuit baord.

My motors are KL23HM276-30-8B Unipolar motors with 2.76V and 3.0Amp per phase. Currently i am using 5V power supply with 50watt 0.33ohm power resistors. With this voltage i am getting 12 IPM. My router is all steel 1000mm x1300mm x200mm and gantry wait is about 40Kg.

Currently I bought 24V 24Amp power supply. I want to use this but the power resistors alone cost $166 US.

Please tell me
a)can i use light bulbs in place of power resistors.?
b) what will be the wattage and configuaration of light bulbs?
c) what forseen IPM can i get?

Best regards

[John3]

I would not use incandescent lamps as resistors!

The resistance increases rather substantially the hotter/brighter the bulb gets. The effect is so strong, people have used them as sources/sinks of constant current no matter what voltage is across them.

If cost is an issue why not make some yourself with nichrome wire?

John

[Khalid]

Dear John3,
How can we make it with Nichrome wire? How the wattage can be calculated? do u have any experience of using it?

[NC Cams]

How to use nichrome:

Go to a table for a nichrome wire source.

Read the ohms/foot or meter for the particular diameter/gage of wire you can get.

Do a bit of math and conjure up the diameter and lenght of wire you need to get the desired resistance. Recall that the resistance WILL change as the temp of wire changes.

Find a place to wind and then dissipate the heat that current flow thru the wire will generate.

Resistor wattage is a function of I*R*R, again, a bit of math is required to figure out that wattage that your home brew resistor will dissipate.

Don't use light bulbs for reasons already cited.

[_Eduardo_]

There are a mistype, the wattage is I*I*R

A 'standard' resistor of 250W is a ceramic tube of 1" diam x 8" long ==> 25 in^2
(Note: At 250W they are very hot).

Roughly, the homebrew resistor will need at least 0.1 in^2 per Watt of dissipative surface.

Eduardo.

[Khalid]

Hmmm... i will try to make those out of nichrome wires... Am i or my circuit/motors safe to use them?
If u have the same issue , do u go to power resistors or self made with nichrome wires?

[harryn]

Have you considered using a linistepper driver ? It is open source and for that motor, would only need 12 V. The entire driver kit is only $ 25 and if you are entirely DIY, all of the PCB layouts and software are free.

It is normally approx 1.5 amps, but I think it can be pushed a bit- that is my plan.