Tag Archive: panel meters


Ahh. Holidays. What better time to fiddle with projects?
Not a lot to report on the project front today. More of a quick update on my analog meters, planned projects and new toys.

Remember last post I talked about making new covers for the meters?
Well! Here they are!

Purty no? On the upside, I learnt GIMP doesn’t like doing colour inversions, but paint does… Riddle me that internet, riddle me that…

That’s the only update I have for you on that project. I have kinda lost some inspiration on the SD card logging when I couldn’t get some example codes working. Just needs more time than I have had recently.

Moving right along!
New projects!
What are several things a electronics hobbyist needs?

  • Soldering Iron
  • Multimeter
  • Oscilloscope
  • Bench Power Supply

Yes? We are in agreement? Ok, maybe not the oscilloscope quite that much, but still. Would be pretty handy…

So I have a solderin iron. It’s old and the tip is burnt through, but it works pretty well. Multimeter? Check. A cheapo $20 one picked up from leading edge electronics when I was 12 I think… Once again. It works to everything I need it to, so far. Oscilloscope? I wish… I’m saving for one at the moment. A cathode ray would be awesome, but I just don’t have the space. So lately I have been thinking of and looking at the digital scopes. As of yet, I don’t know. Peoples thoughts?

Now. Bench power supply. That, I am missing. At the moment I just use the 5V line from my arduino. That’s not really the best way to do things due to the current limitation from that line. We don’t want to be burning out my arduino board now do we? That would just be inconvenient.

So. what to do? A variable bench supply is too expensive. I could mod an ATX powersupply to feed me the 5V and 12V lines from the molex plugs, but the only spare ATX supply I have is dying and they draw a bit of power even with no load attached.
What to do?
Enter brilliant idea.
Build a simple 5V and 3.3V power supply.

Using an LM7805 and a LM317 voltage regulators, feed 12V from an old wall power pack I found lying around into the regulators. Take the output from the LM7805 for 5V, output of LM317 as 3.3V, output direct from the wall pack as 12V. Throw some regulating capacitors and backwards current protector diodes in. Throw a heatsink on the regulators just in case. Simple! I can even build a little adapter to plug in a 9V battery instead of the wall pack. Some pretty LEDs in and switches to turn each segment of the supply on or off. Best idea ever. Best thing is, I have most of the components! Just not the important ones. Like the LM317 and the capacitors… Looks like I’m going back to Jaycar.

After a bit more research I will be ready to draw up a proper cicuit diagram.

Onto my new toy. 😀

Thanks to a post at Hack A Day, I managed to pick up a Texas Instruments experimenter board for half price. Only $13.66! That included shipping! An offer I could not refuse.

The board was a MSP-EXP430FR5739. This board was developed to show off a new(ish) system of memory called FRAM (Ferroelectric Random Access Memory). FRAM boasts a write endurance of 100,000,000,000,000 cycles. What the hell? Thats a huge number. Over 100 billion times more than FLASH memory. That thumb drive with all you back-ups isn’t looking all that safe anymore now is it?
FRAM also writes a hell of a lot faster than FLASH. like, 100 times faster.

You must be thinking, “If FRAM is so good, why do we still use FLASH memory?”
I’m glad you asked that.
While FRAM is more reliable, faster and uses less power, it also have several flaws.
As with all new stuff, It’s expensive! That is the main point in it not taking over FLASH. No one likes spending lots of money, especially big corporations who cut corners to save 1c per product…
Capacity. It just doesn’t, at the moment, have the same capacity for storage compared to FLASH.

That’s enough of me plugging the FRAM. On to plugging the experimenters board infront of me.
This little baby is a 16 bit RISC architecture MCU running at 8MHz. On the board there is a 3 axis accelerometer, a thermistor, 8 LEDs and 2 switches. Other TI boards can be connected to it via a couple of header plugs at the back of the board. All PC and USART conections go through a micro-usb plug at the top of the board. Power is also drawn from USB.

Wow that’s a piss poor photo. Man, I need a new camera…

3 axis accelerometer and a PC interface? I think a gesture control for my PC is on the cards…

Well enough from me today. This short post turned into quite a long one. I should probably go do the washing up now… Have fun!

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Analog RAM and CPU Meters: Update

So I finally found time to fiddle with the CPU and RAM meters again today. Between Uni assignments and The Witcher 2, I haven’t really had much time for hacking, but after finishing The Witcher 2, I had to do something to procrastinate.

So I sat down and wrote a little Python script to grab the current CPU load and RAM usage. To do this, a module needed to be imported into the script. WMI. Windows management instrumentation. Other given modules are also needed. For example, serial and time. So we can actually TALK to the Arduino. You know, I hear that’s handy for what I’m doing…

Source

As you can see, I’m sending the data as a string of characters, with a begin and end byte.

So, I’ve got the data, and I’m pushing it to the Arduino, now all I need to do is get the Arduino to do something with it! Remember those bytes I put in between the data bytes? Yep. Let’s use those to tell the micro controller what data packet is going to which display.
Basically, on Serial.available > 0, we check the byte, if it’s the byte that precedes the CPU byte, we set a flag as 1, if it’s the byte that precedes the RAM byte, we set the flag as 0, if it’s the byte at the end of the stream, do nothing, we don’t need that data. Ultimately I could remove it, but I like having the option for letting the micro controller know that the transmission is finished, but I digress. With any other byte, we check the flag and output the value to the corresponding meter. Simple.

Arduino Source

I originally tried to be all fancy like and send it in 2 data packets with the Most significant nibble of each byte in the first packet, then the least significant byte as the second packet. Basically multiplexing the data. For no real reason but to try and implement something I had learnt in my communications theory class. Well, as you can see, that fell through. The Python script managed to encode and send the data, but for the life of me I couldn’t get the Arduino to decode the data. I’ll probably keep fiddling, but for now, it’s working.

See?

The left meter is RAM and the right is CPU. You can also see where I’m working on the SD card interface.
The CPU output is quite jumpy because the CPU load is changing all the time, I’m working on some action smoothing methods that I can implement on the Arduino, just something else I need to work on.

The final product plan is a mounted set of monitors with LED backlighting and a custom back planes. As you can see, I’m not really measuring mA, so I was planning on scanning in the current back planes and photoshooping some new ones that suit my project, just to give it that finished look.

Yeah I know, I’m avoiding the SD interface. I’m a little daunted by it honestly. But to be fair, I’m avoiding a lot of things, aka, uni work. So on that note, I leave you. Enjoy this quick update!