Raspberry Pi – RISC assessment

browserJust a quick update about my RISC OS experience with the Raspberry Pi. So far I’ve got it connected to the internet and had a quick play around.

The browser that comes pre-installed is called Netsurf. It’s a nice, responsive little browser but is also a little limited. I couldn’t get any javascript to run but I don’t mind too much at the minute.

I installed Firefox through the Store app but found it to be very slow. That may be caused by the fact that I’ve only got the 256mb Pi but I did check the memory manager and it showed plenty of free RAM. Dunno.

LIRCOne thing I have managed to get installed is LIRC. I manually downloaded the package (can’t remember the link at the minute) and installed it to the SD card. There was a font problem initally but though playing around, I seem to have sorted it.

The Pi is now running IRC and I’m sat in the rather excellent #tymkrs chat room.

Now to see if I can find a VNC client…….

Running RISC OS on Raspberry Pi

RiscOSbootWhen I was at my junior school (I think they call it primary school now), we used Acorn BBCs. In fact, we used them in the infants too (mainly to play Granny’s Garden). One morning I arrived at school to find our teacher setting up a brand new computer… An Acorn Archimedes. We used these computers all through junior school and comp. Our school only had a couple of PCs and they were for using Encarta (you had to put the CD in a special little CD caddy).

Because we used the Acorns for so long, I got very used to RISC OS and loved it at the time. I now have my own Acorn A3000 computer although I’ve never managed to use it for one reason or another. I really must look into getting it running.

A3000  Anyway, here is a picture of my A3000 with my raspberry PI sat on top of it.

I’ve had my raspberry Pi for a long time and to be honest, most of the time it’s lived in a drawer. Steve uses his most days for tinkering with but mine’s been sadly neglected… Until now.

I downloaded the RISC OS image a while ago from the official raspberry pi site and it’s sat on my hard drive waiting for me to do something with it. The time is now!!

The installation was just as simple as any other OS install with the Pi. Download the image, run W32 DiskImager and pop the SD card into the Pi. While it’s booting you get a nice boot screen as the one shown above. Once it’s booted, it looks pretty much as it always did.

Apps

I’ve only had a few minutes hands-on time so far but I’m loving the nostalgia.

My plan now is to try and use RISC OS as much as possible and see how I can fit it into my daily tasks. I doubt I’ll be able to administer Windows 2012 servers from it but I’ll have a damn good go :)

Product Review – Peak Atlas ESR70+

esr70-1Around 80% of the faulty electronic devices I look at repairing are caused by faulty electrolytic capacitors. Sometimes you can see a physical fault with a cap (bulges on top or even leaked electrolytic fluid) but often you can’t. The only way I had to test any suspect caps was to simply replace them and test the circuit. This took ages and could end up unnecessarily costly. If only there were a better way……..

Hang on… what’s that? an ESR meter? What’s that then?

An ESR meter measures equivalent series resistance across a capacitor. Basically it’s a magic tool to tell you if your capacitor is any good or not.

I’ve wanted an ESR meter for ages but having never even used one, I didn’t know how useful it would really be….. Until I got one!!!

I got my grubby little mitts on a Peak Atlas ESR70 (or ESR plus, I’m not sure of it’s official name) and have never looked back. I’ll admit, it’s not something I use every day but it’s one of those tools that even if you only used it twice a year, it’d be worth it. In fact, I get a bit giddy every time I do get the chance to use it….. yes, I know that’s sad…

I won’t fill this post with lots of photos, I’ll just point you directly to the products web page. http://www.peakelec.co.uk/acatalog/jz_esr70.html

Anyway, back to the point. The Atlas ESR70 measures both ESR and capacitance. It’s great for checking caps to see if they are even close to the value they have written on them. I know there is a certain tolerance with the values but sometimes you find a cap that clearly isn’t performing as it should and needs to be replaced.

One feature of the ESR70 is that it can test caps in-circuit… but only in certain situations. If the cap is in series with any other caps, the reading will either be off or the meter will kindly tell you that it’s in-circuit. Nice. To be honest, I hardly test my components in circuit now because there always seems to be something that affects the result so I just whip it out and test it but the feature is there and can be useful in certain situations.

The ESR70 couldn’t be simpler to use. You turn it on and connect your capacitor. Simple. The LCD display shows the ESR value pretty much straight away whereas the capacitor value can take a few extra seconds. Once the ESR70 has read the capacitor, it makes a pleasant little “ding-ding” sound. If it finds a capacitor that is too leaky, it only makes one little “pip” sound. The beeps are especially helpful when you can’t look directly at the meter because you’re too busy holding the test probes onto a part. If you leave the unit unused for a few minutes, the meter will automatically turn itself off. This is great for people like me who forget to turn things off and then the next time I go to use it I can’t because it’s 2am and there aren’t any battery shops open……. Please tell me it’s not just me who’s experienced this….

Another useful feature is how the test leads are supplied. The unit has a crocodile clip on each wire but it can be  removed to reveal a mini banana plug. This allows you to take off the crocodile clip and connect a pair of test probes for when you need to get into a tight space. As I test most of my capacitors out of circuit, I hardly ever use this feature but it’s good to have. An extra feature on the ESR70 is that it auto-discharges capacitors before it tests them. Some other meters insist you discharge them manually first… who has time for that??

As good as this meter is, there is a little bit of work you have to do yourself (not just this ESR meter but all ESR meters). The LCD display shows you the ESR reading of the capacitor but you have to look up the result on a chart which is supplied with the ESR70. I’ve printed several of these charts, laminated them and stuck them all over the hackshed so I can read the results at a glance. Basically you find the capacitance and the voltage of the component under test and look it up on the chart. If the ESR shown is lower or very close to the value on the chart, chances are that it’s a good cap. If the results are much higher than the chart suggests, then the component is bin food.

So now you’ve googled ESR meters and found a nice man in China who will sell you one at a seemingly great price on aliexpress. Why shouldn’t you buy that one instead? Well, for the same reason you would rather use a fluke multimeter instead of the one that came free in a box of cornflakes. (Slight exaggeration but you get my drift). I personally wouldn’t want to rely on a piece of test equipment that was thrown together for a few pence and will probably fail within a few months.

Peak Electronic Design Ltd is a British company. It’s Managing Director is a chap called Jeremy Siddons and he’s also the lead engineer within his company. I’ve spoken to him before and it’s immediately obvious that this is a guy who knows his product inside out (he did design it) but more than that, he cares. He cares about his products, his company and most of all, he cares about his customers. If you follow his Twitter feed (@peakatlas), you’ll see his conversations with his customers. It really is important to me that a company cares about it’s customers. Too many companies out there don’t give a toss, once you’ve spent your money, you can leave them alone. Peak isn’t one of those companies.

D-Link is but that’s another story……

Anyway, do yourself a favour – go and buy one. I promise it’ll change your life.

No, I’m not affiliated with Peak Electronic Design in any way and no, I haven’t been paid or asked to do this review. I’ve done it because I firmly believe in credit where credit is due.

 

Quick build – A transistor NOT gate

NOT-GATE

I had a few minutes to spare the other night so I decided to build myself a quick transistor NOT gate. I will be adding other gates to the breadboard and posting their functions on the site but this is something to keep you occupied for now.

First of all, let’s have a look at the schematic of the circuit itself.

not gateWith only 3 resistors and one transistor, it’s easy to build this small circuit into other circuits.

The NOT gate is often called an inverter. Basically, you give it either a 1 or a 0 (on or off) and the output will be the opposite of the input. e.g. if you connect and switch to the input and an LED to the output, when you turn the switch ON, the LED will be OFF. If you turn the switch OFF, the LED will be ON.

Here is a quick picture of the of the circuit I built on a breadboard. (Click the image to get a larger version)

breadnot

Excuse the untidy wiring, I never have time to trim cables and make things look neat, especially on a breadboard. At the top left corner of the board I’ve got a 9v battery connected to a 5v regulator. That then feeds 5v into a 555 timer. The timer is used purely to supply a pulsing on-off signal. I could have easily used a manual switch but I had a 555 chip nearby so I thought I might as well use it. (Same for the voltage regulator). The transistor and resistors lower down on the board are the NOT gate.

When the 555 timer sends an ON signal, the red LED lights up. In the image, you can see that the green LED is currently lit. This is because the red led is NOT on.

When the red LED is lit, the green LED is NOT on. Simple.

Here is a truth table to show a NOT gate.

not-truthBasically, as a recap, if you give the NOT gate a 1 (on) the output will be 0 (off) and vise versa.

Found – Xilinx CPLD chip

I’ve been looking through a few old boards in the parts bin and came across this….

cpldchip

 

 

 

 

 

 

 

It was sat in this board…

1

It’s some sort of ISA CD-ROM card.

I’m now seriously considering building my own board with this chip and building a parallel cable to program it with.

You can never have too many development boards….right?

Logic Gate Simulator

One piece of software that I’ve found invaluable is Logic Gate Simulator.

It can be found here. It was written by a guy named Steve Kollmansberger.

There are probably plenty of other gate simulator programs but this is the first one I found and I love it.

It lets you plonk your gates onto the drawing board and then tie the inputs and outputs together. I highly recommend the program and I suggest you give it a try.

gatesim_ss

 

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