Winners Announcement: Ben Heck's Raspberry Pi Bitscope Mod!

A Transistor, capacitor, resistor, inductor checker.

Maybe it could even test LEDs.

So, using an Arduino, current clamps and some electronic parts, develop a device that can limit the current that's flowing into the grid coming from a grid-connected-inverter that is powered by solar batteries. The limiter should control an electronic potentiometer. Make it work for three phase grid. Each phase should be controlled independently. Also measure the power, generated from solar panels/ batteries, the power used to charge the batteries, the power sent to the grid from the solar panels, the power used from the grid, in a three phase system. With possibility to log the data and send the data to a website to visualize the data. All built around an Arduino or similar. Make it cheap to build but accurate and safe. Also use the weather forecast to do stuff like defining when to charge the batteries with a generator. So it is possible to go off-grid.

I am working away on Better Lockdown system.  I want the RPi to be able to test and display proof that my class workshops have all been locked down in the event of a lockdown drill.

I Work in a school that does lockdown drills, however in the workshop we are having issues meeting all the requirements.

1. cover all windows - we have 35 windows

2. Lock All Doors

3. Notify all members of lockdown/drill

the plan is to setup 35 window blinds with motors that allow the blinds to be lowered and raised via a light switch (when we just need to darken the shop) or via the master alert.

The master alert is a SMS message recieved by an Raspberry Pi that starts a series of events.

1. lowers all blinds, blinds are on a track with a sensor at the bottom that can indicate that the blind is lowered

2. sends an sms to all persons on a whitelist that the lockdown is in effect.

3. engages the lock switches on all doors and sets a 15 second timer to release the fire door magnets

4. sends an SMS to the Vice Principal that confirms the shop is locked down after all blinds and doors are closed.  if the hallway motion sensor is linked as well it will also update via sms if any motion is detected in the halls.

so in essence it is a system that acts and tests its own effectiveness

alternatively, the same setup can be used to confirm that I have shut down the work shop properly at the end of the day.

Well I doubt this will count for 2 reasons: 1) It isn't necessarily test equipment but rather a framework to incorporate test equipment into a single device. 2) Chances are I won't build it due to complexity and my poor soldering skills.

You could think of it like a rack with back plane but for test equipment. Maybe a good examples would be a large blade server, or even similar to pci expansion on a computer. Truth be told; the idea originally came from hunting my multi-meter while working on a blade server. I thought why don't I have a desktop multi-meter, wait why would I want a desktop multi-meter and oscilloscope, wait do they make devices that do both, wait what about a logic analyzer, wait couldn't the same device be signal generator, wait why wouldn't you have the test equipment provide proper power, wait I can't afford any of this stuff, and finally I give up. Then it hit me that a blade server is rather good way to have an expandable desk lab.

When you break down the actual functional boards or components of each device they are relatively small. Newer oscilloscopes (one of the larger pieces of desktop equipment) are mostly dedicated to everything else but the testing circuitry.

So the idea is

Hardware

1) You have what amounts to a computer(probably an rpi) that runs the software and drives the display, audio, input, output, etc. It provides the data bus for the back plane.

2) You over engineer a clean multi channel power supply. I am not fully sure if an individual channel per-device is required but being test equipment I would assume so. In any case from this you provide some basic voltages. to the power "bus" for each module. 3.3v 5v 9v 12v Clean-Raw for example. The goal being to provide the most useful voltages so modules aren't having to inefficiently convert it for each module.

3) You put a large touch screen on it with some common useful hardware buttons and switches. I could see on the high-end using small lcd displays to label things.

4) An eject and select button under each module slot.

5) The modules would simply have what ever connectors are valid for it's function on the outside. They would connect into the back plane. Each module would provide what ever functionality is required to convert the data it takes in into something it's software driver could understand. You would imagine that a lot of this could be done in a boiler plate way to make it easier, faster, and cheaper.

Software

1) It would probably be easiest to have a single program running on Linux that would act as the "operating system". Although, I myself would likely do the opposite and build drivers for the modules and try and use native Linux features as much as possible.

2) If using Linux natively you will need to create a service that watches for the select buttons and activates the appropriate interface command string or sends the appropriate signal to the display application or something. Else the "OS" will need to monitor for this.

3) If you are just making dynamic libraries for a single app version of the host program then you would incorporate the driver into this somehow, else you would want to create drivers and incorporate those into Linux.

4) In either case you will need either a program, dynamic library, template, or something to determine how information is displayed on the screen, as well as any configurable hardware user interface buttons.

5) Like in 4 you will also need something to handle any output that the device needs to be sent. Especially true if said device stays active even when not selected.

My reason for preferring to use Linux natively is that the chances of the whole system failing is small. Some modules like a power supply module may lead to a bad time if say your program crashed. I touched on another issue too in Software:5 in that some modules will need continued activity. Maybe all of them will. So it would be far easier to let an operating system built for multi-tasking handle such things than you try to do it yourself. The only potential issue I could see is that a RTOS kernel maybe required.

There are some serious caveats.

> The speed in which some of the test equipment needs to run may run up the costs a great deal or make it outright impossible to be built outside of a large corporation.

> The speed required may also mean that a cheap solution like an RPI is not sufficient. I could see this in something like logging data.

> A solution like this particularly is never going to be as accurate as a real purpose built device.

> The power supply is going to be difficult and expensive. Also well beyond my capabilities, and I would hazard a guess that building it for safety is likely outside of many other peoples capabilities also.

> The software will be fairly complex. At a minimum you are looking at developing a very robust and generic API and interfacing with Linux hardware devices. On the heavy end you could be writing drivers and firmware for your custom built pci-e devices.

> If the speed is an issue and you must move to something more robust like pci-e, then you can expect that soldering will become nearly an impossible task. Which means very complex manufactured pcbs.

> Probably many things that I haven't considered.

As a radio ham I would rather like to have kind of a spectrum analyser. Unfortunately these are real expensive. Now with the advent of software defined radio there are cheaper ways to monitor the output  spectrum of our home brew equipment.

I found a very nice idea at adafruit (https://learn.adafruit.com/freq-show-raspberry-pi-rtl-sdr-scanner/overview ) where a SDR-RTL TV dongle is used to display the spectrum between 25 and 1800 MHz.

I replicated that design using a Raspberry Pi with 7 inch display (like Ben used in the Bitscope project) in a Smart Pi Touch case. Here is a video of my project:

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It would be great though, to enhance this design with:

• an upconverter to cover the lower frequency bands (qrp-gaijin: RTL-SDR upconversion with diode-ring mixer: part 2).
• shielding the dongle to protect it from interference.
• adding BNC and/or N connectors.
• add selectable input attenuation (50 ohm).
• put everything in a nice case like Ben did for the bitscope project.

I'm really sure that Ben is able to create a great project out of this idea.

Given that ethernet is still safer than wifi and often faster too, my idea is a test tool for network cables. These are quite expensive (besides the most basic ones) and probably beyond the reach of most users.

First it must be able to test that all cable cores are connected correctly. Second it has to do some throughput testing or what it is called to see that it can handle a connection without errors. Maybe it can even test if a ethernet outlet or cable is connected in the other end and if so at what speed.

It will probably be powered by a Raspberry Pi or an Arduino or something like that, have a display, and be able to generate some sort of report after testing. If it can even print a label it will be awesome.

Today all tablets excluding apples . All tablet  feature older arm Cortex cores means less performance. And less r & d on tablet I want to mod a tablet cpu. With more powerful arm Cortex cpu . A bitscope is a powerful tool for this idea . And convert this idea to a great mod.

Follow up:

Instead of LM317 IC's for the controllable current sink, I've found NPN power transistors to be a suitable replacement, which provide a constant current draw (regardless of supply voltage) for a fixed base current, and obviously it is cheaper to use transistors than LM317 chips..

Most Arduinos have an analog voltage resolution of about 4.9mV which is not accurate enough for charging 18650's reliably, which is why a separate ADC should be used to monitor cell voltage. Since my project is only interested in discharging cells, the ADC of an arduino would be accurate enough, as the minimum voltage an 18650 goes to is not nearly as important as the maximum.

The reasons, other than the one mentioned above, as to why I am omitting charging of 18650 batteries is to minimise circuitry (large power supply and lithium charging ICs are not required), and cost of manufacturing whilst also maximising the quantity of batteries that can be tested. What I mean by this is that if the recently discharged battery is charged again in the same device, one battery could potentially take over twice as long to test. There are already numerous examples of cheap, multiple cell lithium chargers on the market, so separating the charging and discharging operations maximises the amount of batteries that can be tested in a certain time period.

Thanks again.

My test equipment idea is for a 18650 Cell Tester.

The idea behind it is that it would take 4 cells, charge  each one individually as well as discharge each one individually. Once the discharge is complete it would then recharge them.

The data can then be collected via a small LCD screen as well as possibly sending it to a computer to graph each cell. This project would be build upon an Arduino Mega or ATmega1284.

The idea for this project came about from my work giving me a whole heap of old laptop batteries to do with as I please. Ideally I would like to see what ones are worth keeping and recycle them into other projects.

So saving the Earth from e-waste, and recycling them into new projects.

in the office building I work we have DIY addressable led strips surrounding every floor of the building to make it glow at night. It's a part of my job to maintain this setup and unfortunately the setup breaks down a lot.

We we got a defect then I have to open up the sealing and get the 3m long led bar out and take it to the warehouse to test the led strip. I have already bought a wireless soldering iron so I can do small repairs without taking the led strip out of the sealing, but I still need to get it out if I want to connect it to the test unit.

It would really be great if I would have sort of a portable addressable led strip tester, that can run the following tests

- put all led's to red

- put all led's to green

- put all led's to blue

- put all led's to white

- slow nightrider mode 1 led at a time

- put all led's to black (off)

this would save me a lot of time and I guess it would be a great tool for everyone that uses addressable led strips in there projects