R.I.P. LCD. Hello OLED?

Organic LED (OLED) technology is one of those things that seems to have been on the way for years. It was going to replace LCD tech at a sweep, with ultra sharp, high contrast goodness. Like many such things, it never managed to take the world by storm, but it still has it's own advantages and disadvantages. I have kept meaning to investigate OLEDs for a while so (with one eye on the LCR meter project) I finally got my finger out and blagged a Densitron DD-12864YO-3A from Farnell Element-14.

Yeah, memorable name. You might guess though, that it is 128x64 pixels, and (monochrome) yellow. I'm used to conventional LCD modules, where a 128x64 might be 100x50mm (4in x 2in) and I had read the data sheet, but I don't think I was ready for quite how small this wee beastie is:

This instantly raises an issue over the form factor. I guess it is technology intended for mobile phones, but for practical hand held test gear I think it is just a bit too small. You can get 256x64 units which are approximately twice the width, but they are twice the price too, and well into the territory of colour LCD with integrated touch panel.

I had intended to hack this straight into an Arduino or Mbed, and get a quick demo running, but a few things have stopped me. See that connector in the photo above? 24 pins, each half a millimetre apart - clearly influenced by it's mobile phone background. None of this standard 0.1" header LCD here! Even with the matching socket, it really needs a custom PCB to break out the lines. Fear not though, I have a cunning plan, which involves a load of 30AWG (0.4mm) Kynar wire.This alone is going to slow down take-up when it comes to amateur projects and even professional prototyping. Secondly, though, the module is 3.3V only. No 5V here, no sir. A few resistors should sort that problem out, but it all adds up. Having said that, I don't know of any commercial systems that run 5V any more, so it is no big issue for non-Arduino folks.

One part of the manufacturer's data informs me that I need an externally generated 12V supply, but another part tells me that it can be generated internally. We shall see.

Looking at the pinouts, it seems like it is an adaptation of the classic HD44780 chip. It isn't. It uses an SSD1305 which does waaaay more than the old chip. Unfortunately this means it takes a lot more driving too. Just booting it up takes a fairly hefty code sequence. The user can elect (by variously grounding 2 pins) to use a classic 8bit 68xx or 80xx parallel protocol or, more interestingly, use 4-wire SPI or 2-wire I2C. If the manufacturers had desired, they could have easily halved the pin-count by going serial only, and removing three "No connection" pins that they insist should be grounded. I'm sure the market for breakout boards with a boost power supply and a level converter is already out there.

So, this looks like an interesting little adventure. I can think of a few projects where a module like this would be useful, not least my JTAG adaptor. It is definitely the sort of thing I will bear in mind for future designs, possibly filling in for indicator LEDs rather than low current LCD (the OLED unit draws up to 55mA). I hope to have some shots of a demo up soon.

Thanks go out to Farnell Element-14 for supplying the Densitron DD-12864YO-3A.

Arduino - DIY Electronics for the 21st Century?

Over the past year or two, it has felt like you can't turn a page in a tech magazine, or read a web page about electronics without some reference to the Arduino. Somehow it seems to have moved from serious "difficult" electronics, into an everyday commodity.

Thus far, I had resisted the Arduino's allure. I don't have any experience with Atmega processors, my usual preference is for one of the Microchip PIC families or, if more power is needed, an ARM cored device. But how could I give an opinion without owning one and having a play around with it? I was impatient as usual, and the people at Farnell / Element-14 had one sitting on my desk within 24 hours. Excellent.

The Arduino Uno

I will go into more details later, but here is a quick rundown.

The Arduino Uno is a totally open source embedded development board, based around the Atmel Atmega328. Other "flavours" of Arduino are available, usually based around other Atmega chips. Arduino isn't just limited to the hardware, however. It also covers the development environment which, to my mind, is the crucial factor in it's success.

The Arduino Development Environment
(Click for larger image)

As you can see from the screen grab above, this isn't Microsoft Visual Studio. Thank goodness. Simple and clean with syntax highlighting. This is why Arduino has taken off.

The Uno itself measures just 53x69mm, and arrives in a simple cardboard box that looks more like a packet of cigarettes or condoms. No. Really. The accompanying leaflet covers the usual legal disclaimers and little more. It would be nice if it said "Congratulations on your new Arduino, now download your free development software from www.arduino.cc" or similar.

It is powered via the standard USB "B" socket, or via a jack socket. I find it odd that they haven't moved over to a mini or micro USB, but no great shakes. The general standard of construction is solid, as you might expect with a mature product, the CPU being a socketed 28-pin DIP/DIL device. This is so you can remove it after programming, or plug it into a breadboard. Or, I suppose, replace it if you toast it.

There is a HUGE amount of resources for the Arduino around the Internet. Almost too many. If you are interested in seeing what it can do, and how easy it is to use, then I recommend Jeremy Blum's YouTube series here.

I got mine from Farnell / Element-14, who stock a range of Arduinos and related gear.

The Arduino Uno I reviewed is available here http://uk.farnell.com/arduino/a000046/board-arduino-uno/dp/1848687

Arduino's home is at arduino.cc

John's Tronix Stuff tutorials here.


Additional: If anyone has any good Arduino tutorial sites they would like me to add, simply add a comment or drop me a line.

Tektronix DMM4020 Bench-top Digital Multi Meter - First Impressions

This is an initial overview of the Tektronix DMM4020  Bench-top Digital Multimeter.

This overview was originally written for Element-14 and is available here. 

http://uk.farnell.com/tektronix/dmm4020/multimeter-bench-5-5-digits/dp/1771901

http://www.tek.com/products/digital-multimeter/dmm4020/

Unit Price:    £528.00  

I must stress that this is just an initial overview.  The DMM4020  is very much a professional piece of test equipment and needs to be used properly in a work context for some time before I can give a thorough in-depth review. Nevertheless, in the short time that I have had it, I have already learned more than enough to give a good overview.

A few month ago, I had considered that a good bench meter should really go on my list of test gear. Less than a week after its arrival, I wonder how on earth I managed without one. After all, hand-held multimeters are really good now and - it has to be said - more than good enough for most work. So why has a bench meter already earned its place in my lab?  Read on…

The meter arrived in sturdy double-layer manufacturer’s box measuring 9”x12”x17”. Inside is a pair of vacuum formed foam blocks which sandwich the meter and provided good impact protection on its journey here. It is the sort of packaging that is worth keeping for storage, should you need to move it around or keep it safe.

Unless you have a huge bench or a permanent place in a rack, then this meter does take up quite a bit of space, being 9 inches wide and 13 inches front-to-back (although it is tiny in comparison to the high end calibration lab stuff). Traditionally though, bench gear like this does appreciate being left switched on permanently, to allow the temperatures to stabilise, minimise thermal cycles and prevent any moisture affecting components as the lab cools down over night. Unfortunately the DMM4020  has a fluorescent display, which has a tendency to fade when left on for extended periods (years). I have not yet discovered a way to turn the display off whilst keeping the electronics running. There is a “soft” power button on the front panel which may well perform a similar function. That is definitely something to investigate. Otherwise, though, the VFD is bright, sharp and fast to react, probably better than LCD could give.

However, this is jumping ahead slightly. The very first thing that I saw – a printed manual. Yes folks, real paper, with print on it. Spiral bound. Hallelujah! Only 26 pages of it are in English (the rest is Japanese and Chinese). It is only a “Safety And Installation” Manual, but it covers the main functions and accuracy tables. The full User Manual is 110 pages but unfortunately only available in PDF format. I will go more into the contents of this manual in the full review. The S&I manual states that power consumption averages  10 Watts, with a maximum of 15 Watts. Each side of the case is  plentifully supplied with ventilation holes, and having left the DMM4020   on for 6 hours, the temperature stabilised just above ambient. It runs  very cool indeed for mains powered gear.

Caution!

There are two things to watch out for before you start. Most importantly, the DMM4020  uses a conventional transformer power supply which is supplied configured for 110V.

It takes until page 10 of the Installation Guide before it mentions line voltage selection. I imagine almost all users will know to check this first, but in a world where people are increasingly used to switched mode power supplies that take 100-240V without configuration, a caution sticker would probably be wise. The actual method of voltage selection is a bit odd but nevertheless functional; You unclip and remove a module which has the mains fuse and a plastic “spider” inside, which is rotated to suit 100, 120, 220 or 240V and re-inserted. Despite having a mains transformer, the unit only weighs a modest 2.1kg

Secondly, the supplied mains cable has a US standard plug. This is not a problem though, as the connector is a standard IEC “kettle lead” and most labs have plenty of those hanging around! The DMM4020  does have a set of stand-off feet moulded into the rear of the case, which allows it to be operated vertically rather than in the conventional horizontal manner.  Unfortunately the supplied mains lead is a “straight through” rather than a 90 degree elbow, and so if you try to stand the meter upright, whether against the floor, desk or slotted into a rack, it sits on the cable rather than the feet, and so is unstable. Note to Tektronix : Supply a 90 degree "Elbow" power lead please!

One thing which is really good to see – a proper mains on/off switch mounted next to the power connector. So far as I can see from looking through the ventilation holes, this is a proper switch which isolates all internal components.

Construction

As you can see from the photo, the DM4020 comes in Tektronix corporate colour. That familiar grey-blue colour which is so often seen around labs. The main body is pressed alloy construction, with plastic front panel. The front and rear both have flexible plastic/rubber protective “boots” which can be removed for rack mounting. As usual with this sort of equipment, there is a tilting bail which can be positioned in a number of angles, used as a carrying handle, or removed entirely. The HRC fuses are of the high quality you would expect, and are accessible by removing a small metal panel underneath the unit. A small plastic box covers the fuses themselves, presumably for insulation and blast containment.  They don’t seem as well protected as they are in hand-held meters.

Internally

I don’t intend to take the DMM4020  apart, not least because that would entail breaking the calibration seals, which I am loathe to do. Fortunately, however, you can get a pretty good view of the insides just by looking through the ventilation slots. This is very much a unit for a clean lab and not a dusty shop floor which would risk contaminating the sensitive electronics in no time.

Visible in the middle off the board is the heated precision voltage reference, clearly labelled LM399H with a National Semiconductor logo. A well known and well respected precision voltage source, used in several meters in this market segment.  Interesting that they didn’t choose an LM199 or LM299 which seem to be 2% initial tolerance versus the LM399’s 5%, although it has to be said that after calibration there is little difference. I suspect that putting the unit into standby from the front panel will keep the heater running inside the voltage reference whilst powering down the display and processor. This would seem an ideal compromise.

In use.

As you can see from the front panel, the Tektronix DMM4020  is a 5 ½ digit unit, with separate connections for low (200mA) and high current (10A) ranges. It is also capable of full 4-wire resistance measurement, although only a pair of Tek TL710 conventional probes are supplied. Supplied probes are usually low budget affairs, but these are really nice sharp Cat III/Cat IV 10A probes with finger shields. However - no ground clip is provided! This is definitely an oversight in a meter of this stature.

One feature I will certainly be looking at is the ability to take two measurements at the same time, or sequentially. Some meters can perform functions such as AC voltage + Frequency, but not many can perform current + voltage measurements together, or DC+AC, such as might be used to monitor power supply ripple.

You will note that it does not measure inductance or capacitance. I guess at this end of the market you would be expected to purchase a separate LCR meter.

Performance

These are the easiest to quantify in hard numbers. All this data is copied from the official (copious) Tektronix information, boiled down into the main points. I will go into more depth in the main review:

Measurement Speed

The DMM2040 can measure at 2.5, 20 or 100 samples per second. Normally 2.5 is perfectly sufficient, and 20 cannot be distinguished by human eye. However, this is good for capturing short transition events, or for high speed logging via the computer link. In the faster two modes, however, precision is truncated by one digit.

DC Voltage

Maximum input: 1000V
Input bias current: <30pA @ 25C
Input impedance: >10G Ohms (200mV and 2V ranges)  10M Ohms (20/200/1000V ranges)
Resolution on 200mV scale: 1uV
Accuracy:    +0.01% of reading + 0.003% of range

 

AC Voltage (True RMS)

Maximum input: 1000V peak, 750V RMS.
Accuracy (all ranges 45Hz – 20kHz): 0.15% of reading + 0.05% of range

 

DC Current

Input protection: 11A/1000V and 440mA/1000V fuses

Shunt resistance: 0.01 Ohms (2A and 10A ranges)
                           1 Ohm (20mA and 200mA)

Resolution:         200uA scale: 1nA (yes, that’s 1 nanoAmp)

Accuracy:           typ. 2mA scale 0.015% of reading + 0.005% of range

 

AC Current:

AC Filter Bandwidth: 20Hz – 100kHz
Maximum Crest Factor 3:1 at full scale
Resolution:  20mA scale: 0.1uA (100nA)

Accuracy:  Typ. 200mA scale, 45Hz-2kHz: 0.25% of reading + 0.05% of range.

 

Resistance

Specification for 4-wire function or 2-wire with REL (relative measurement)
Input protection: 1000V on all ranges
Resolution:         200 Ohm scale :  0.001 Ohm (1 milli-Ohm)

Frequency:

Range: 20Hz – 1MHz, for input >100mV
Accuracy: 0.01%

Continuity:

Threshold: 20 Ohms
Test current: 1mA

Unseen performance

So much for the book data. With less than a week’s use, it is safe to say that I haven’t even scratched the surface on what the DMM4020  can do, but I have found some very nice functionality that most users just wouldn’t notice unless they were looking for. Specifically:

Diode test.

Most diode test functions only work at 1-1.5V, enough to test ordinary signal diodes, but not enough to test LEDs. The DMM4020  reads up to 1.9999V and drives up to 0.8mA, sufficient for the LED to light quite brightly. In theory this is only enough for red /yellow/green LEDs, but in practise the unit will illuminate blue and white LEDs also, which I was not expecting, although it will not give a voltage measurement for these.

Zero-burden Microammeter.

Most engineers will be aware that the usual way of measuring current is to insert a small resistance into the circuit and measure the voltage drop across it. At low currents this can be quite a high resistance, leading to a “burden” voltage drop which is unacceptable and may even upset the circuit under test.

The correct way to do this is with a transimpedance amplifier which provides almost no voltage drop, but can only realistically be performed at low current levels. It is quite a complicated thing to get right in a design and, as a result, is only usually seen in expensive dedicated microammeters. The Tektronix DM4020 is the only meter that I know of (this side of £1000 anyway)  which uses this preferred method for measurement. If you often measure low currents, this feature alone may be worth the price of the meter.

Relay Range Switching.

In order to switch in appropriate shunts and multipliers, the DMM4020  uses proper electromechanical relays rather than silicon switches. This slows down auto ranging, but not unacceptably so. Manual override is always available and is probably preferred in most cases. Relay switching is by far the best method in equipment where you are looking for measurement performance and have the luxury of a large PCB real estate and a mains power supply.

“Other Stuff”

The supplied LabView software is a little clunky to install (and partially deactivates after a preview period) but does work pretty well. I am no LabView expert, but I can see how relatively easy it is to automate tasks if you are working in a production environment. This is definitely one thing I will be looking more closely at. Simply logging data in ASCII format to a text file is very handy indeed.

In order to connect the DMM4020  to the outside world, it is fitted with a standard RS232 port at the rear. Tektronix thoughtfully provide an RS232-to-USB adaptor, with a good 2M of cable. This seems to be based on an FTDI chip, which in my experience has proven most reliable in this sort of role. Windows 7 picked it up straight away and downloaded drivers via Windows Update.

Conclusion

So there we are. Four days use and a “quick” look that is already several pages long. That gives you an idea about what sort of machine the Tektronix DMM4020  is, I hope that I have at least been able to give a taste of what this machine can do. I hope to have a much more in-depth review up in a few weeks, after it has had some use in a real world situation. One of the things I have lined up is the development of my LCR meter project. Having a meter this accurate will help immensely.

A Request

I want to shoot some video of the DMM4020  in action if I can. At the moment I only have a webcam and a cheap compact camera that will shoot video, so I am looking to buy myself a reasonable 720 or 1080 digital video camera. Does anyone have any recommendations? I don’t want to spend more than maybe £150 or so, it doesn’t need to be a fantastic spec. Thanks!

Additional: Farnell / Element-14 tell me that UK purchasers will have their meter pre-configured for UK 240V power.

HP-15C now in Stock at HP! No it isn't! Yes it is ! No it isn't!

Well, the HP-15C finally made it to market, and promptly sold out within a few hours. So quickly, in fact, that I didn't even get a chance to post it here before they had all gone. From the look of Ebay, many seem to be bought by speculators.

Anyway, they are back on sale at HP's online store. Oh wait... No they aren't. This time the stock lasted about half a day. All I can say is - keep an eye out for when they restock! My guess is that if they keep selling this quickly, then the Limited Edition won't be quite so limited.

Amazon.com look to have them in stock. 4 left at the time of writing, listed at a mere $119:99. $20 more than the official HP shop, albeit Amazon have free shipping. Can we say "gouging"? I thought so. Still, it is cheaper than Ebay.

I don't think I will be buying one, I find the missing binary / hex modes too useful. Any chance of the HP-16C? Potential purchasers might like to be aware that the build quality is typical Kinpo Electronics rather than classic Hewlett Packard.

A PCB CAD Refresher Course

At one time it felt like I was destined to be a PCB designer, churning out design after design for someone else's work. Now this is a very worthwhile and skilled job, but it wasn't for me, and so it is only occasionally that I get to design PCBs now. Unfortunately that means that I tend to forget work-flows, and fiddly little quirks and details. Come to think of it, I tend to forget some pretty big details too! When you have let muscle memory get on with things, it can be daunting when you come back to your CAD software.

I have a fair few notes which I have written up over the years, and I was even considering recording a video. This started me wondering what YouTube might have to offer. Altium have done a load of videos (hosted on their own site), but I have to say they aren't very helpful. At best they are rather "corporate". Anyway, to cut a long story short, I found these YouTube videos. They are clearly recorded by someone who knows what he is doing, and aimed at the more introductory end, but are very much worth watching if you need a quick refresher.


All these videos relate to Altium Designer, and are best viewed full screen. Videos recorded by http://www.youtube.com/user/elektroniskorg

1. Schematic capture and PCB layout (Part 1)

2.Schematic capture and PCB layout (Part 2)

3. Creating a Component Library

 
4. Navigating Designs

5. Working with Vias and Multiple Layers

6. Copper Planes and Pours

Advanced Calculations

(Or how 1989 - 2011 = 15+30+34+41 )

Thanks to Make Magazine Blog for mentioning my article on calculators (see Difficult Calculations ). It seems that I am not alone in my calculator geekery. Page views shot up by a factor of 100x in a couple of hours!

Inevitably though, no sooner had I written the article than things started to move on. It looks like Hewlett Packard aren't totally devoid of sense after all. Thanks to Dave Jones of the EEVBlog for pointing me in the direction of this:

Yes, this is from the real Hewlett Packard web site. This is a screenshot of the Google cache (see here) of HP's Singapore web site. (Screenshotted just in case the cache gets overwritten) Similar pages were on other nations HP sites too, including the Indian version. I checked, and it all looks legitimate and not a spoof. At the time of writing, HP still hosts a photograph of the calculator in question, an HP-15C:

HP-15C Limited Edition

Investigations by the forum members at the HP Museum site have revealed that the "HP-15C Limited Edition" will shortly be on sale in Japan. No information is available as to whether they will be shipping them in other countries.If they do appear in the UK, then one is going straight on my shopping list.

It looks like a pretty close copy of the original, but the brushed aluminium bezel around the display has been replaced with what looks like white plastic, and the printing somehow looks less crisp. My guess is that Kinpo have been brought in once again by HP, and rather than simply producing a copy of the original, they have re-engineered it to maximise cost savings. Something which has rather back-fired on them in the past. As it stands, the (still in production) HP-12C internals have been converted to an ARM processor based system for some time, so a new version of the 15C and 16C should be straight forward.

Back in the 80s, the HP-15C cost $135. It looks like the new version will sell for an RRP of $129. That is fine in the US, the land of discounts and coupons, but I suspect it will come out at £129 here in the UK after taxes. Given that the HP-15C is based the same hardware used by the HP-12C ($70) then it starts to look a bit expensive. It is a shame that they didn't go the extra mile and produce the HP-16C too, which adds binary and hexadecimal functionality.

The WP-34S

It looks like the HP-12C re-purposing project (that's the polite term for hacking now) has stalled (see here) but the project to investigate the potential of the HP-20B and HP-30B business calculators seems to have moved onwards very quickly indeed (see here), enabling vastly more functionality, based around the HP-42S core software, but very much expanded upon. In fact, it does so much more, that the developers have had to print a whole new set of key legends:

Original HP-30b

Modified with WP-34SFirmware and key legends

Yes, these are the same calculator. I do wonder just how robust the stickers are, but reports seem generally favourable. A complete reprogrammed calculator + overlays is on sale at £76:98 / €84:68.  The firmware manual / user guide is available here.

Do you know what I love about it though? It has markings on the keys - and this is the important bit - I don't know what they all mean. Seriously, I have a row of letters after my name, I have been doing engineering maths for decades, but yet there is stuff in there that is a mystery to me. Sure, it is statistical stuff that I will never need, but that doesn't matter, it means someone is finally adding new functionality to calculators. It makes me feel a bit like when I was a kid with my nose pressed against the window of the glass cabinet with all those mystical electronic boxes inside.

So that is 15, 30, and 34 dealt with (see the blog title), how about 41?

Well, processor designer Monte J. Dalrymple has reverse engineered the HP-41C, and then created an improved version of it on an FPGA. I mean - seriously - it doesn't get much more hardcore than that does it?

Lots more information here on Monte's site. 

The thing is, all the essential hardware is on an FPGA. It is a relatively (and I use the term recklessly) easy job to hook up your own LCD and keypad, and you have your own HP-41C clone. All it needs is a millionaire willing to stump up enough money to make moulds for the enclosure. Some things have simply got to be done.

Suddenly, the world of calculators just got more interesting.

Hewlett-Packard Calculator Timeline

As part of my previous blog post on calculators, I had started to draw up a graphical representation of calculator evolution. My intention was to include TI, Sharp, Casio etc (hence the timeline starting at 1960) but considering this subset of HP calculators took several hours, I decided a full comparison probably wasn't worth the effort. Given the popularity of the previous item, I thought some people may be interested. It doesn't include all HP calculators by any means, finishing with the HP-48S.

Hewlett-Packard Calculator Timeline