Looking for a high wattage resitor

Maybe I missed it. Searching here and everywhere I found a wire round resistor and a cement resistor for 5W. I need just a larger normal resistor, like a 3W metal film. I wondered if there was an easy way to just make a 1/4W bigger or I could find the actual part already made. Thanks.

No you didn’t miss it. There aren’t a lot of different resistors in Fritzing. As to making a part, yes it is possible (I wouldn’t call it easy except perhaps for me :slight_smile: ) to change the standard resistor part. Making parts is fairly complex and requires you to know a variety of constraints and requirements to get the part correct. First we need to get a data sheet (hint: posting the datasheet of the part you need is a good start!) so I searched for 3W metal film resistor with google and came up with this datasheet from digikey:

where this part is the FMP3WS 3W part (and hopefully matches what you want.) That gives me the size of the resistor body and the diameter of the pins (and it appears that it should fit in the same 0.035in hole used for the standard resistor) and the spacing of 0.8in between pads. So I increased the size of the standard resistor body by editing the breadboard svg file in Inkscape and modified the body and legs. It is a bit complicated because the basic resistor has bendable legs which complicates the part like this (this is the breadboard svg displayed in Inkscape):

Here the connector0pin (red arrow and highlighted in xml editor) must be a rectangle, and outside the viewbox (green arrow) as must connector1pin on the other side of the resistor. Then

connector0leg must be a path, must start outside the viewbox and enclose connector0pin and end inside the viewbox. The schematic svg is identical to the standard resistor and doesn’t change. Pcb needs to be moved from 0.4in spacing to 0.8in spacing on the pads and have the body size increased to match the larger resistor (it may have also needed the hole size to increase but did not in this case!) Then some changes to the .fzp file need to be made so the part stays a part of the resistor family (so the code will change the color bands when the value is changed in Inspector) and a new variant assigned (in this case I changed variant 1 to variant 3W to indicate 3 Watt) and added 3W metal film to the description field. All of that results in this part which when loaded in to Fritzing should do what you want.

edit: Figured out the problem, the moduleId needs to be in a different order. This part works correctly!

Resistor-3W-metal-film.fzpz (4.6 KB)

which looks like this compared to a standard 1/4w resistor

Although even with that it doesn’t work quite correctly, you can not select the value in Inspector (I don’t know why, but will poke at it and see if I can fix it!) The new part should be able to select the value in Inspector like this (and change the color codes):

but it is greyed out and I don’t know why. The layout in pcb won’t be affected, only the display of the value.

Edit: Figured out the problem and replaced the part. The moduleId needed to be in a different order to trip the color code value code (had to check the source code to see what moduleId it was looking for!). Now it works correctly:


Instead a custom part, the standard resistor in core parts may work. Changing the pin spacing in Inspector adjusts the PCB foot print, but not the breadboard view. The bendable leads help there though. The power box in inspector does not have any other dropdown choices, but it does allow a new value to be typed in.

If this works for your needs, adjusting each resistor one at a time can a nusiance. Instead, place one resistor, adjust its settings to suit you, then duplicate it to create the others.

I figured out that the moduleId order was incorrect and have now replaced the part with one that works correctly via an edit of the original post. The source is looking for the moduleId to end in “ResistorModuleID” and I was adding characters at the end which broke it. Using “3W-ResistorModuleID” works.


Thanks to both of you. Peter, are you a god? :wink:

I’d say definitely no :slight_smile: , I have a lot of experience making parts for the last 6 or 7 years, and most of the folks I learned from no longer post. I’m basically hopeless at development though. I can sometimes read the source (as in this case to find what moduleId it was expecting) but changing it generally eludes me. So I usually make parts for folks (as that needs experience to be successful.)