Half Ohm - milliohm adapter
Half Ohm milliohm adapter is ready! Multimeter adapter that transforms any multimeter into a precision milliohm meter and debugging device. Notice that your multimeter is useless when measuring small resistances, like connectors or tracks. So did I, so I built this: 1% precise, small and cheap adapter for you. Ultra useful for finding position of shorts on your board. I have already used it tens of times. Get one!
Milliohm meter in connected
Usage:
- Connect the adapter to your multimeter and power both of them.
- Half Ohm should light up brightly.
- Switch multimeter to voltage range.
- When nothing is connected, you can read the battery voltage. Battery is 3V CR2032, so if the voltage is lower than 2.6V, consider changing the battery.
- When connected with a resistance smaller than 1Ω the voltage in mV shows measurement in mΩ. So 1mV = 1mΩ, 10mV = 10mΩ and so on.
- Connect your probes to adapter and connect them both with each other (press into one pad or something like that) the readout is more or less the resistance of your probes, connections and meter itself. Zero that with RELATIVE button or just memorise it.
- Measure the real thing, the difference between last and this measurement is your resistance.
The back side
Finding position of short circuits:
Connect and power everything. Press your probes to shorted tracks. Probe around. The direction where the resistance decreases is the direction of the short.
Calibration:
If you want to test or calibrate the adapter then you can use 100mΩ resistor that is included. On the bottom edge of the PCB there is big 1206 100mΩ 1% resistor that you can measure.
The sources:
Schematic and board in KiCad. My KiCad libraries! Schematic in PDF.
I am using much free software and I though to recommend some better ones. Like all linux programs, they all run on Window and maybe even Mac.
- KiCad- The best free electronics CAD
- http://www.kicadlib.org/ - Good source for libraries
- http://kicad.rohrbacher.net - online library part and module generator
- http://cyclerecorder.org/footprintbuilder/ - module generator
- http://jaanus.tech-thing.org/everything-thats-not-hardware/tech-thing-kicad-library-manager/ - library manager
- Gerbv - View you gerbers and delete unwanted parts
- gerbmerge - Merge your gerbers to one big panel
- Visolate - Gerber to milling optimized gcode "It will truly violates your eyes."
- Printrun - Controlling printer and sending gcode to it.
- Falstad circuit simulator - Simulate simple electronics with perfect components. Perfect for learning and testing simple things.
- HTerm - Terminal client. It hates processors, but the GUI is too useful to hate it.
- FreeCAD - Big and feature rich open source 3D CAD
- HeeksCAD - Easy free 3D CAD
- SMath Studio - Free and cross platformish MathCad clone.
- Geany - Good and fast IDE for every languange.
- yEd - Best graph making program I have used. Use every time you encounter documentation.
Screenshot of Tech-thing KiCad Library editor
The KiCad default library is so messy. Sorting and editing everything with text editor is pain in the ass (atleast possible *hint at eagle*). I tried to download some existing library managers, but none of them worked. So... I made my own.
Tech-thing KiCad library manager manages both, the library files and module files. It lets browse all your library and module files and their content. You can delete and add files. Also delete, rename, copy and move their content. Supports library components with aliases, just use / between aliases (example: OPA334/OPA2334/OPA335/OPA2335). To use it, copy it to KiCad base folder and run it with python.
The code is made in python, using tkinter. I tried to make it readable and pretty but it ended up as always. At the moment it's at version 1.0 because it has all the functionality I wanted it to have, maybe sometime in the future, if there is an interest for it, I will continue developing it, but not this week.
Ideas:
v1.1 add file rename button
v1.2 make it easier to run on different operating systems
v1.3 refactor the code with askstring(...)
v1.4 make it possible to copy modules from board files
v1.5 add whole library viewer
v1.6 add search
v1.x maybe add more parameters to edit in each component (3d file location etc.)
v2.0 display pictures of each component
Source in Github
So I finally forced myself to try KiCad, yes, forced, their user interface is really so horrible. I decided to try KiCad because its one of the biggest open source EDA programs. Another option was gEDA, but KiCad looked friendlier. The reason I went away from EagleCAD is because it is controlled and owned by evil corporation. Its free and juicy today, but tomorrow you want to sell something you designed with it and you can't unless you pay 50$ (or 1494$ for full version).
First I had to make the schematic. I chose small and easy schematic - Attiny13, some pinheads and capacitors. Because It didn't had Attiny13 by default, I downloaded Attiny library from http://www.kicadlib.org/ . Adding the lib was bearable. Adding the components was.. good? I liked the shortcuts version more than Eagles command line communication. But the user experience at whole was terrible. The graphic lagged behind, there were artifacts on the screen all the time. GUI and buttons were a little old looking and .. random. I wanted to add six same connectors and I had to click add button (a) every time. But like, searching from library was better than in Eagle. When moving components the wires stay in position what is silly.. But whatever, actually I love the library idea in there, totally makes sense and is logical. And the ERC is times better than Eagle.
KiCAD schematic editor with basic circuit.
So next I had to annotate, sound reasonable, but why do I need separate dialog. I probably will use it a million times the configuration can be in preferences or wherever. Next fight with netlist generator. I didn't get that. Why do I have to press four buttons to generate nets. Not like there is more than one way to generate those. And later, I wanted to generate new version of netlist and there was no Save button, only Save As. WTF, I still have the same project, I change the components for like 20 times before I'm satisfied, why should you Save As, stupid!
After that - CvPcb. Basically you assign the footprints to components. I think that this is great idea, it brings down time to draw new components. And that IS important, because if you do something else than LED+Resistor+555 then you run into components/footprints/etc that is not in library. And it has online symbol generator too, brilliant. So tried to match my polarized capacitor to package, after trying all of the packages I gave up and took the SIL package. The GUI was frustrating again. I have to press some ultrasmall button in order to see what the package looks like. Totally not starter friendly. Although if you use it daily you will remember all of the packages. Later I found out that right polarized cap packages were available online. So.. I download the package and its useless, I need some random webpage's help even to make the most basic schematic. Bad. Then I chose DIL for AtTiny and started to look package for my 3 pin connectors. I tried about 3 different packages before it got to me that SIL (Single-in-line) is the thing I want. Again, Eagle has ruined my logic and simplicity of world. I just hate library management in Eagle, like, stupid.
PCB Board
Finally, routing. I moved everything to place (I love those shortcuts) and started routing. First thing I noticed was the trace width: it was too narrow. So I read my tutorial, try to follow it, but there is no such menus. I find three more tutorials and still, I can't find such menus. I had different version! So half an hour of manual searching and menu digging later, still nothing. Okay, whatever, I can live with that. Routing was a bit stiff but nothing worth mentioning. The graphical things crashed, showed ghost airwires and made some other airwires invisible.. Again. Annoying. But I managed it, even the ground plane took only three tries to make.
So, KiCAd, I want to like you, but yea. There is just too many cliches, bugs and not enough user friendliness in it. But it is so close. If the developers would focus on GUI for a week and left that stupid autorouter to wherever it is then it would be real competition to Eagle. Good job!