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Topics - arakis

General discussion / Electronics theory question
Here Is a question to which I almost failed my first year Electronics exam :D

If you have a 12V battery hooked up in series to a forward biased "real" diode with the (Vd 0.6v) and a capacitor. what will the capacitor voltage be if it is assumed an infinite time period passed, and the capacitor and battery are ideal case(no parallel or series resistance)?
General discussion / Dangerous 3D Models
We've started to build SketchUp 3D models of our projects. We use the EagleUp script.

You can find the models we've built so far in our SVN. You need to download them into the directory that's linked by the EagleUP script...

More part models will be uploaded soon..If you'd like to donate some of your models plz post them in this thread , just compress them with your favorite archiver and upload them to this thread. Or link to their 3d warehouse link, if you've already uploaded them there. Pictures are welcome as well.

The eagle up script builds everything at 1000X scale, so 1mm is can post files in different scale as well.

We will also try and upload all the components to the 3D warehouse at some point...

As always any comments, suggestions,ideas, or questions are very welcome..
General discussion / short Reset signal for 3310 lcds
I have a Nokia 3310 LCD, now for it to function properly it requires to be initialized with a short reset pulse....Does anyone know how to accomplish this without using a uC pin...something simple a resistor-capacitor, or even a transistor. I know how to do it with a 555 timer, but that's defeats the purpose...
Project development, ideas, and suggestions / Dangerous Soldering Iron driver V1.5(based on Arhi's gen3)
We really liked Arhi's SID gen we decided to build our own. We allready build a Version 1 which was based on his gen2 but a few bugs were found out, and corrected. so now here is the Soldering Iron Driver V1.5. Its based on arhis Gen3.
Read about his project, and development here...
Read about our version here: ... evelopment

This driver is capable of driving all soldering irons based on RTC, J or K type thermocouples...ITs been tested on Hakko, Gordak, Solomon, and Weller soldering irons....
Bus Pirate Development / Adding a mode to the BP firmwate
Hi all, I'd like to try out writing some special feature mode to the bus pirate.

Now my coding skill is relatively limited, I mean I can read and write code...but that's about it. Since I am new to the Bus Pirate firmware It looks rather over whelming trying to figure out just the basic function calls.

The feature I would like to make is a PC-fan testing type thigie :)

simply put it should use the same basic PWM mode, with the added RPM, and Voltage measurement.
So you type in the frequency and duty cycle on AUX, and the BP reports back the RPMs (frequency of pulses in minutes) on AUX1. it should also report the voltage on the ADC pin as well.... ( I am building a PWM driven DC/DC converter that would drive the 3pin Fans, hence the-need for the voltage).

I guess this could be easy be implemented with a short script, but the whole point is that I would like to get familiar with the BP4 code, to get my baring straight so to speak.

So my question is how should I go around adding another mode to the bus pirate, ( this is just an exercise so I wont commit anything to the SVN, but I will release my code here). Any help at all will be much appreciated. Thanks
Bus Pirate Support / Bus Pirate installation
Well this is embarrassing, I have both the 3.5 and the V4 Bus pirates and I cant get either to be recognized by Windows 7 64bit. I used the inf file in the DP SVN to no effect.
Project logs / DP Digital Multimeter
Here is a new project we are thinking of attacking. A digital multimeter...
To start of we would make it simple, and easy to build and prototype, to play around with.

Here is what we think would be nice for version 1, but as with all our projects input is both encouraged and in some cases needed :)

*(+/-)Volt,Ohm,(+/-)amp meter (both AC and DC)
*controlled with a microcontroller (with usb)
*Microcontroler will control the ranging, although probably manually at first and auto later.
*possible app to follow it..

those are the basics we want to get right first, once we figure out haw to implement them, sky will be the limit.

below are a few schematics we found on the net of commercial DMMs
General discussion / Viewplot gerber preview
Before you send your gerbers to the PCB house it is always a good idea to check them over, I use viewplot. The thing I would like to know is what are the common errors that can be picked up by viewing gerbers? So far I never found an error
Project logs / SILtheDIL
Seeing as many MCU demonstration boards use DIL pin headers on either side of a board, which is impossible to implement into a Breadboard. I decided to make a rather crude and simple adapter that converts 2X20 DIL to a 1x40 SIL.

The 2x20 header could be female or male, depending if you want to stick your module directly into the adapter, or use a cheap HDD ATA 40 ribbon cable.. here are the pics and eagle files for the project. The pics were taken before the boards were cleaned of flux, so lots of brown gooey stuff is there :D
Project development, ideas, and suggestions / TQFP 100 Break out for Microchip devices
Wanting to built a breakout for the PIC24f256 in a 100 pin TQFT package to play around with, a came across the fact that most microchip devices taht have a usb and are in the tqfo 100 pack , use exactly the same pins for basic setup.

VDD, VSS,AVDD, AVSS, VCORE, ICSP, and USB pins are all the same, so the board I was making for the pic 24, is usable with pic32, dspic33s as well.

the board is setup so all the component other then the pic and usb are on the bottom layer, to make it easy to route and solder the pic. Added bonus is that it could be manufactured with only the pic unpopulated, thus instantly having a working breakout for any of those listed microchip devices.
Project development, ideas, and suggestions / Slow 8 channel USB analog data logger
This seems like a easy and cheap project to do, and even at 10KS/s sampling rates it would find many uses, especially for people starting in electronics design.
To allow a user to simultaneously watch and compare up to 8 analog signals in real time on the computer.
Make it as cheap as possible. 
A singe MCU is all that is needed to both read the channels and pipe the data through the USB.
I think pic 24F have a sampling rates of 500KS/s, the PIC32 1MSps.

Minimum amount of external components, probably only a few resistors for the voltage divider and a few switches or mosfats to change the range. 20V 2V would probably be sufficient, although if needed a few channels could have a analog front end to read down to 200mVs.
A external reference would be used to allow greater precision

Have the USB connector broken out to pins to allow internal motherboard connection.

Question, how fast could a PIC24F and PIC32F read 8 channels and send the data to the computer, what kind of sample rates could I expect, I am also interested if the sample rates could be increased by lowering the amount of inputs.
Project development, ideas, and suggestions / Help with a 3pin Fan controler
Hi I would like to design a fan controller for PC fans that use only 3 pins.
GND, VCC, and RPM.

If you PWM drive the VCC you lose the RPM, there is a possibility of stretching a pulse from time to time just to read the RPM, but this brings audible noise into the fan. So I think driving via PWM is impossible. Although if you have any suggestions I would love to hear them.

Liner driving via PWM is covered by this Maxim http:// note, but the problem with liner driving is power dissipation in the output transistor. I would use either P mos, or PNP in a to220 package.
the circuit could be able to provide 500mA of current, which is around 6W if the fan gets stuck and draws 500ma at 1v, then the Transistor will take the full 6W on it self and I don't think it could handle it without a heat-sink.

Would soldering the back of a To-220 to the board provide enough of a heat sink to handle 6W?

Any suggestions how this could be designed without the use of heats sinks?