10 September 2017

Redraw Analog Meter scale with Inkscape

A dual-needle clock.
Guess what? I've had a challenging idea of a (clock) project, and it has suddenly become top priority. Because of the new challenge.

I want to make a clock using a dual needle analog meter. Ideally an SWR meter would be converted into this analog clock. Electronically speaking, with an Arduino and a couple of PWM outputs, interfacing is simple. A few lines of code and you're done.

The challenge lies in redrawing meter scales. The easy part requires to scan the original panel detached from the meter, and then it is all a learning expeerience.

Once you compute that the needle moves over an angle of 60 degrees with a radius of about 48 mm, both scales have to be drawn with proper marks: one every hour or five minutes.

Old fashioned way: draw it by hand. Fun and relaxing, but not too professional looking.

Test printout.
Do it on the computer: how? A drawing software is needed. Possibly free. And with layers so that the original scan can be used as a reference. Something in the back of my mind suggests that I need a vector graphic software and the search engine response is: Inkscape. It runs on Windows, Mac and Linux.
Not willing to install software for a one-time project on "main" home computers, I turn to the 10-year old HP Pavillon laptop on which I installed Ubuntu Linux 12.04. Once I head to the package manager and search for Inkspace I am welcomed with a warm "Already Installed" message.
The Internet is full of tutorials, but Inkscape itself is well documented too. In two hours I manage to redraw my scales the way I want and I even get the size right at the first printout. All for free.
The original scale (on plastic) vs. redrawn.
By the way, the laptop is a Core2Duo with 1.5 GB RAM and 120 GB HDD (dv6236ea Frankenstein). It runs LibreOffice just right. Firefox surfs the Internet without a problem and I can watch HD videos full screen off YouTube because the NVIDIA graphic card is fully supported. Arduino IDE works too and ... Dropbox (which does not work anymore on WinXP)!

06 August 2017

A cute VFD display

At the Marzagla rally I spotted a small box with a 7-segment symbol and "Nixie", all hand drawn/written. Inside there were three small 9-digit VFD's looking NOS. Five € for the three.

The display looked like the Russian IV-18 and IV-21, with all pins on one side, but they have no external markings and one extra digit. So they are not an IV-21. To simplify things these tubes had an insulator slipped over filament wires: that left [9 + (7+1) =] 17 more wires to idenfity (9 digits, 7 segments, 1 decimal point).

Back side. No markings!
The visual area is about 3.5 cm, and the whole tube is about 6.5 cm long. I can make a desktop clock/display since you won't be able to read at a distance.0

Since the filament was already identified, I began from it. I started at about 1Vdc and raised it in partial darkness in order to observe if the filament would start to glow (not good, sign of too much current). I settled at 1.5V and started looking for segments and digits. A good news is that it glows even at 12 V, so I will have not to worry of having and dealing with a higher voltage as most VFDs require (30 V, some even more).


Spreading the wires.
Luckily grid pins are on one side and segments on the other. Not willing to design a PCB for this display I took advantage of the long leads and build a simple adapter on veroboard. I will chop off the extra board under the display and let it hang out of some sort of vertical structure .... when I will be done with all the electronics involved.

A not-so-quick and dirty adapter.

18 July 2017

32600 Li-Ion batteries

Not much is going on this Summer 2017: it is just too hot! Meanwhile a friend gave me a couple of battery packs from a burglar alarm system. They get replaced yearly during periodic service. The label states Li-ion, 2x 3.6 V 13 Ah. Pretty little beast: it can almost direct-drive a bunch of while LEDs and make a lot of light, or last very long. But all contacts measured 0 V, or open circuit. Time to... pry it open!

I was expecting to see some 1SxP configuration and instead I found two 32600 cells. They are huge, like D batteries. Also they are not connected in parallel.

I recall that some Li-Ion batteries have an embedded protection circuit from over-(dis)charging, that disconnects the battery (= open circuit, or 0 V) when it is too low. In fact once I fed some 4V to each cell it sprang to life and started charging.
32600 vs AA

Unfortunately there do not seem to be cheap flashlights that can host this cell size (32600 or the more common and slightly longer 32650), so I will have to build mine. If this cell has a capacity close to 6000 mAh, I can run a 1W while LED for about 15 hours, or a normal 5 mm LED for 300 to 600 hours! Or a booster to 5V makes it a bulky powerbank.

Well, I spoke too soon. Since it already happened to me that a Li-Ion element started self-discharging and self-heating, I was periodically checking voltage under charge and no-load as well as temperature (to the touch). It went like this. Both elements stabilised at 3.96V. When I removed the charging source the voltage dropped steadily down to 3.60V,  about -1 mV/s. At 3.6 V thereabout they heated up, warm to the touch. Voltage stable. After one hour they were ambient temperature and reading 0 V again.

I will not bother with the second pack and bring them both to the recycling center.


15 June 2017

My take on CloudAtCost surprise maintenance fee

Note: this post goes beyond the interest of the main audience of this blog. But it is the only way I have to share my thoughts. If you have no business with CloudAtCost you can skip this post. But please don't do business with them.

Few years ago I bought a virtual server from a company called CloudAtCost. It was sold with a one-time risible fee that left me wonder what kind of business model was behind it. Now, on June 15th 2017, chickens are coming home to roost. I received an email from them titled "24 Hour Server Suspension Warning" stating that there is an unpaid invoice. So I logged into their user panel to discover that they changed their Terms of Service, and now they include a recurring annual maintenance fee (9 USD). The invoice was issued one month ago, and no email warning had been sent. Also, as I recall, no email warning was issued when ToS were modified.

Over these years their service has been quite lousy, and got worse month after month: I could live without my overseas basic server.

But but but.

I have an invoice of 9 USD expiring in a couple of days. I looked everywhere on their user portal for an "account termination" button, but I couldn't find any. I took the time to read their current ToS and found these worringly interesting points:

9.9 All bills and receipts will be sent to Customer electronically at the current email address provided by Customer in the Customer Account. Customer is responsible to keep such email address up to date with CloudatCost. [NOTE: I got no bill for the maintenance fee, but first pay then complain - in 30 days - ]

9.11 Interest will accrue on any amount not paid for thirty (30) days following the billing date, as and from the billing date at a rate of 2% per month (26.82% per annum) or the maximum legal rate, if less.

9.18 Customers with a onetime payment service is subject to an annual maintenance fee of $9 which will be invoiced 12 months after using our service. This does not apply to users that have a monthly paid service. This Maintenance fee will ensure proper hardware upgrades and maintenance to reduce degradation of onetime payment services. [this generated the current mess]

And, last but not least:

20.1 The terms of this Agreement, including fees, charges, features, content or any other aspects of a Service, may change at any time and without prior notice. The Customer is responsible for frequently reviewing this Agreement posted on CloudatCost' web site to obtain timely notice of any such changes.

Paragraph 20.1 struck me: they don't care to notify their Customers of ToS changes! And they can change the fee of §9.18 anytime, without giving any notice. I am speechless.

Given their Customer-unfriendly manners, I have a strong feeling that all those unpaid maintenance fee invoices generated by "forgotten" accounts will end up at a debt collection firm(s), together with the 26.82% interest rate: what a great way to financially support their "business". A note to European users: their debt would be transferred to a EU-based firm and then subject to EU laws. Improbable? Maybe. But in 5 years such a debt could turn into a request of 100€/$.

My strategy is to pay the invoice and begin the account termination procedure in due time. UNLESS, they REALLY improve their service.

12 June 2017

5870 vs 5750

Nixies 5870/ZM1332 (and alike) and B-5750 share the same pinout, the same digit dimensions and shape, but not the height. Here is a side-by-side comparison of the two tubes during a test in my clock-to-be.

Left are ZM1332/5870's and the rightmost is a 5750:

Left to right: ZM1332, ZM1332, ZM1332, B-5750.

26 May 2017

Staging the Nixie line-up on PCB

First things first: do ZM1332/5870S fit and align on my fresh PCB's? Do they look right? In order to get a first impression I picked four of those Nixies and inserted them into one PCB.

Probably the holes in the footprint I made in KiCad could have been a tad larger. Nixie pins need to be 100% straight to enter, but the black plastic base can be pulled down to keep them aligned. On the other hand, the little beauties stand up perfecly: good when I will solder them to the PCB.

Front view.

Top view.

Back view.

23 May 2017

My firstpcb.com's first PCB's have arrived!

Finally! After a slooooow journey across the world, my first PCB's have arrived! Ten pieces of a board holding 4x ZM1332/5870S Nixies, the driver IC and transistors. The tubes are supposed to be multiplexed offboard.

There is a lot of free board space, I know. I could have packed many more components, but I really wanted something as general purpose as possible that would simply hold the tubes in place at a proper distance. And, a PCB that would work right away (test still pending).

These PCBs were designed in KiCad and fabbed by www.firstpcb.com. I haven't found a problem but, as I said, these are simple two-layer boards.

In case you want to give a try at the whole PCB production process, you may want to register through my referral link https://www.firstPCB.com/mi_odrCr8 which gives both of us a 10 USD bonus (new customers get it nevertheless).

The boards packed in vacuum. Cool.