Gettings ready for the weekend

Yesterday I realized I have “collected” too many fans from computers and some electronics. I decided to see what I could salvage from them and toss the rest. Twelve out of the twenty or so fans have ball bearings. I saved the bearings and wire harnesses. The rest of the fans are junk. I just cut off the magic wire to the coils and tossed the wire into my recycle pile.

I also tried slapping a crude power supply together. The transformer pushes 20 volts at 1.5 amps. Yet when I put on a load such as a regulator the voltage drops to 0.23 volts and the amps increase to 1.10 amps. I works fine powering a PC 80mm fan but anything else it just freaks out. Guess I can use it for a soldering fume extractor.

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Did a few things

Tired out some molds for the HDPE. Works well but I need some more clamps for the center of the mold. In all it works well. The mold is the size of typical printer paper. Even though it isn’t that big it still takes a bit of plastic, I used a heaping butter bowl full to get a single blank.

I had to rearrange the room a bit today. I was playing some good old SimCity and the youngest boy came running in and hit the plug causing the computer to turn off. My stupid self didn’t save at all. The new placement is far better since now I have a wall to hang stuff let alone more storage since I reconfigured the table setup.

Payday I plan to order some LM317 adjustable regulators and try and build a adjustable power supply replacement.

RC Car controller

Last year for the heck of it I bought a cheap RC car from walmart and thought to myself what if I made it faster. The standalone controller can’t do it because of the small low power transistors to the H-Bridge.
A while back I stripped down a broken RC car one of the kids had and been sitting in a junk box since. I pulled it out and sure enough it’s also 27MHz and I was able to find some info on the main IC. The IC is a SDRX2BD made by SuperChip. The datasheet I found also has a example schematic on how to test it let alone to build a simple controller. Pins 10 and 11 control the reverse and forward function. All I have to do is lift the two pins on the controller then build a bigger H-bridge to pump more power into the motor. I don’t have to do anything to the left and right movement since it works well.
I can always change the left/right function later if need be.

I hate standstills with projects

All of my projects are currently on standstills until I can get one or two things for them to finish let alone get further on them.

With the CNC I need some material to make molds for the HDPE parts. Until then I’m collecting more plastic parts/bits.
The peer to peer dial-up is became boring let alone if I continued I need a couple of ATA boxes to add onto a PBX server.
Arduinoscope is on hold until I can order some parts to make it embedded.

Currently I’m just showing my little girl some fun things with electronics. Yesterday I showed her how a small motor works and how if you reverse the polarity it will make it turn the opposite way. She had fun and played with it until the battery died. I think next I’ll show her how to use LEDs and then make a nightlight or small flashlight. Hard part will be showing her how to read a resistor chart. Might just print one and use some color pencils to make things easier.

Passing on knowledge

I am a step father of four. Two teens and two younger kids that are 8 and 7 years of age. I tried to start on the path on teaching the youngest boy but in all he doesn’t have the intentions to learn. The teenagers are typical zombies with playing video games on their laptops and getting them to do anything is like pulling teeth with plastic pliers. However I noticed the youngest child Elyssa has been interested, she asks questions and such. Yesterday I was going through the junk on my desk and tossed out a template of a case and some how she grabbed it and tossed a fan in it. Then she asked me if I would teach her “How to build stuff”. I said sure but I don’t know, her mother is kinda iffy. In a nutshell she doesn’t want her to be a “tomboy”.

So i’ll just teach her some things such as automotive primitive tasks such as changing a tire and checking the fluids. How to use a ruler and measuring tape. Of course electronics. Might even show her how to use glues, adhesives and paints.

I asked her if she is ready to learn hard stuff that school won’t teach and she said yes. So it will be tricky but I know she will get it since she does very well in school. She attends to over achieve. In the meantime this might inspire her bother to learn as well since they attend to copy each other.

News and DSO138 follow up

This Friday and Saturday I plan to start on building a case for my Arduino scope and attempt to make a PCB for it. I’m going to make the case expandable so in the future I can add other options. The case will be made out of HDPE with a sheet metal cage on the interior.

I also plan if possible to stop at the local DRMO and see what they have in electronic test gear if they even have anything. Or I’ll just cruise craigslist and find something.

I have given up on the DSO138 problem. JYE confirmed the PCB to my DSO138 is a counterfeit and Banggood.com says otherwise and doesn’t want to budge so I dismantled the PCB and salvaged parts from it. I doubt I’ll ever order from them again. Now I need to find a home for the LCD in a project down the road. Wish I can find more info on the LCD module so if I choose to use a AVR I could find the proper library if one is needed. The BNC connector is going to the Arduino scope and the rest are just jellybean parts.

cleaning up a EMI/RF mess

When you’re on the last steps of completing a project such as a AVR based Oscilloscope you attend to run into issues such as interference from AC mains voltage or even your WiFi network. Reason being is all electronics produce a sound signal. For a example a typical home in the U.S. will push out 60Hz. Since the device I am building will use a small power supply from AC mains I have to take some extra steps on making sure I don’t have trash noise going into the device. This trash I speak of is called “Ripple”. If you use batteries then you do not need to worry about the Ripple. Ripple is leftover noise from AC rectified to DC.

When looking on a Oscilloscope AC looks like a sine wave and DC is a straight clean line. A full bridge rectifier will swap the sine wave of AC and turn it into a DC signal but a very bumpy ride so to speak. This is called pulsing DC and for something like this to power a AVR let alone a DIY scope this is a bad thing. To smooth out the bumpy mess of pulsing DC we need to filter it. There are a few ways to do this but the easiest is with capacitors. Now this is with a Linear prospective. With switch mode power supplies it goes in more depth and can really make your head hurt.

When using one or two capacitors to filter out ripple this is when a scope is handy so you can properly get the correct mixture so to speak. The capacitor charges when the pulse hits around the peak and carries the charge for the next peak of the signal.

Example:
120 volt 60Hz mains with a transformer dropping the voltage to 6 volts 60Hz. Add Four 1n4001 diodes to make a full wave bridge rectifier to convert to DC. This will turn the DC output to 6 volts 120Hz.

Look at the bottom left sine wave, that is typical AC. Look at the bottom right. That is typical pulse DC. Since the rectifier has turned the AC down stroke signal and pulls it up. Now when we add the filter capacitor it turns the pulse DC into more of a clean signal.

The red line is the DC straighting out becoming a cleaner signal. Now you can only get so far and you’ll need a regulator to make it a true clean signal. So you will end up with something like this.

Yes, this is a typical linear power supply with a regulator. A lot of novices don’t know this. It’s the fact you get a clean signal in you’ll get a clean signal out. In this case since this is for a AVR it will be harder for a messy signal bleeding into the input voltage of the device.

Now for EMI/RF on other parts of a device. I had to look around some HAM radio sites for this info. All electronics not only produce sound but also produce radiation and also receive interference from sounds and radiation. This is why most home consumer products have metal cases or have metal shielding all over the place. This helps the device to block interference. There are several ways to shield a project. You can use a metal shielded case/enclosure, EMI/RF paint, smae stuff that is found inside phones, tablets and even laptops to reduce weight. If you have time on your hands and a decent scope you can use ferrite beads. I never know that that ferrite cores had a special color coding. Different colors are form different grades of material the core is made from and used for certain things. The typical dark gray type are for suppressing signals typically found on computer cables. I use them for video signals and long data lines and will come in handy for my DIY AVR scope. To use a metal shield it’s nothing more then conducive sheet metal and attached to chassis ground. HAM radio users prefer copper and the paint stuff is nickel or copper conductive ink. You could get away with foil but I wouldn’t use aluminum/tin, it’s better to use copper foil that is mostly found in arts and craft stores.

Hanging up the Arduino for now

Spent most of the day trying to make a menu system for the TVout library and failed big time. However I tweaked the TVout Oscilloscope sketch so it refreshes a little faster. Since the DSO138 was a bust and I really want a decent scope I decided to just stick with the Arduino scope sketch. Not too bad really and since I’m using the TVout library I can easily expand later by adding a second Arduino and still be able to use the single LCD with two AVRs. All I would need is a switch to switch between the video output.

Now since the software portion is complete I need to embed the AVR to be a standalone and also make a case for it. To minimize AC feedback noise I need to use a shielded case and probably toss on a few ferrites. Might also have to add a cap or two to minimize ripple.

Tomorrow I’ll toss up a few examples of minimizing AC noise and EMI noise.

Playing with the Arduino

I’ve been intrigued with building a small bench style portable lab using the Arduino. Since the Arduino has built in ADC (Analog to Digital Converter) I built a simple DC voltmeter. Now since I have gotten a better grasp on programming the thing I am seeing how far I can go on creating a menu system and select between a Voltage Meter and Ohms Meter that can be displayed on a 7 inch TFT LCD with the TVout library. If I can make the code super small I can add other features such as a soldering station controller and maybe some sort of Oscilloscope or even a power supply controller. It’s not the IO count I’m worried about but the size of the code. Would be nice if I can load a compiled Arduino sketch from a SD card but I don’t know where to start and some of the premade code from other authors doesn’t fit the bill.