I bought a couple of ‘generic’ micro SD cards on eBay about a year ago. They were not much cheaper than brand name cards, and though only speed 6 rated, were available locally for quick delivery. I have a vague recollection that it might have been a RPi product supplied with NOOBS on it (I have a couple of SD adapters with the RPi logo on them).
These were both used in RPi B systems and worked without fault for the last year, though they are not running full time (perhaps a couple of hundred hours of use).
During a Raspbian sofware update, both cards failed with the same problem, they effectively became read-only cards. Continue reading Micro SD card premature failure
Some while ago I purchased a EZP2013 device programmer on eBay.
There were literally scores of sellers, and they all looked the same, and some variation in price from about US$25 to US$50… which is not unusual.
I used the thing a few times, and it was clearly a very poor product so I replaced it with a SOFI SP-8B which cost close to US$50 on Aliexpress including a bunch of (6) adapters. Continue reading Chinese counterfeiters at it again – EZP2013
Seeing the promotion of a clear adhesive with cure initiated by ~400nm UV light from a LED source, one’s mind wondered to its application for attaching temperature sensors to heatsinks etc.
A sample of Kafuter K-300 was tested.
Above is the test jig, a 1N4004 diode is attached to the corner of a scrap of 1.6mm thick aluminium sheet using the adhesive which was cured with UV light and then allowed 10 hours further to strengthen (if that helps). Continue reading UV cure adhesive for temperature sensors
I use a number of implementations of the DS1307 or DS3231 Real Time Clock chip, preferably the latter these days as they are considerably more accurate and compatible with DS1307 code.
In some applications, it is necessary or sometimes just better to preset the clock before connecting it into the application, and the need arises to set the clock ‘stand alone’. The method I have used for this has been clumsy and not as accurate as one might want for the DS3231, so this article describes a new solution.
The solution uses an Arduino as the engine if you like. Above is an Arduino Pro, but a range of similar Arduinos would be equally suitable. ALso pictured are three RTCs, one connected to pins A2, A3, A4 and A5 providing GND, VCC, SDA and CLK respectively. Continue reading Arduino app to set DS1307 Real Time Clocks.
This article documents initial tests on a MultiStar 5200mAh 3S Lipo.
Two of these were purchased for about A$24 ea + delivery from the HK Australian warehouse.
On delivery, the batteries were served a balance charge to full capacity.
Above, one of the batteries with the usual mods to suit my quadcopters. A heavy heatshrink encapsulation to reduce the risk of battery damage from crashes and flying propeller bits, rocks etc. A little velcro path to help stabilise the battery on the quad, a ‘gripper’ for the balance plug, balance plug secured to keep it out of the props, and a charge indicator for convenience.
Continue reading MultiStar 5200mAh 3S Lipo – initial tests
Fox flasher MkII – owenduffy.net described an animal deterrent based on an STC 8051 microcontroller and running from a single LiPo cell.
This article describes a further development using a solar cell, shunt regulator, 1S LiPo cell with protection board, and two high power red LEDs.
Above, the unit constructed in a medium size Jiffy box, and a 6V 0.6W PV panel fixed to the top with silicone adhesive. The LDR is fixed to one end with silicone adhesive.
Two SM 1W red LEDs are fitted to opposite sides. They are 120° LEDs, the holes are countersunk to provide for light dispersion and the LEDs clamped to the inside with small brass brackets and heat sink rubber, a little silicone adhesive seals the holes. Continue reading Fox flasher MkII – high power 2 LED solar powered beacon
This article describes a build of the PIC Iambic Keyer (PIK).
Above is the generic circuit diagram of the PIK.
This one runs on 4.5V from 3 x AA cells. A 3000mAh battery will run it in ‘sleep’ mode for around 2,000,000 hours or 230 years… the shelf life of the batteries determines their useful life and there is consequently no ON/OFF switch.
So, the variation to the circuit above is that the zener regulator circuit is not required, Z1 is omitted and R5 is replaced by a 50mA Polyfuse. C3 is 0.0068µF to give a range of 6-36WPM on 4.5V.
Above, the internals. The electronics is assembled on a small piece of Veroboard with jacks at the rear for paddle, hand key and output, a pot for speed control and switches for TUNE and AutoSpace.
Above is the external view of the keyer prior to labelling.
Browsing eBay for some high power LEDs for a current project created frustration in trying to wade through the stated performance figures (to they extent that they can be relied upon).
LEDs are often headlined as having some luminous intensity in candelas, but while that might seem to be a good measure of the ‘brightness’ of the LED viewed on-axis, it gives no information about the spatial distribution off-axis and the total luminous flux output or flux density.
I wrote a little online calculator that can be of assistance in finding the total luminous flux and flux density give luminous intensity and apex angle, Calculate luminous flux (lm) from luminous intensity (cd) and apex angle (°). (Note that specified luminous intensity is usually on axis and should be discounted by perhaps 20% to provide an average luminous intensity over the cone angle.)
An example, an eBay seller advertises:
Source Material: InGaN !
Emitting Colour: 0.5W 10MM HI POWER White 0.5W LED
LENS Type: Water clear
Luminous Intensity-MCD: Typ: 290,000 mcd
Reverse Voltage: 5.0 V
DC Forward Voltage: 3.2 ~ 3.4V
DC Forward Current: 100mA
Viewing Angle: 40 degree
Lead Soldering Temp: 260¡ãC for 5 seconds
Power Dissipation: 500mW
Does it appear rational? Lets calculate average luminous intensity at 80% of 290cd, 232cd. Lets assume the viewing angle is the half power beamwidth.
Above is a calculation from the specifications. Of concern is the calculated luminous efficiency of 266lm/W, it is perhaps three times or more the expected value, so it questions the accuracy of the claims. Even at 0.5W input, the luminous efficiency is unrealistically high. Continue reading Making sense of LED output figures
I made a couple of picnic tables about 35 years ago. The design was broadly inspired by picnic tables deployed by the ACT administration at the time (local government), it used a galvanised water pipe frame for table and integral seats and hardwood tops.
I kept one of these tables, and the hardwood eventually degraded sufficiently to warrant replacement.
Durable timber has become very expensive, and the choice limited. Red Ironbark (a eucalypt endemic to the forests south east of here), GOS (green off saw) and DAR (dressed all round) was chosen, and stacked in the shed for a couple of years to dry down to 10% moisture content.
The timber was washed down, trimmed and edged, drilled and oiled (Organoil, a naturally drying oil mix), and fixed to the table with 304 stainless countersunk socket head M8 screws and nyloc nuts.
Above, the refurbished table. Total mass is 125kg, about half of that is in the hardwood and the rest in the steel frame.
The table will required replenishment of the oil finish every year, but should be a durable non-toxic lasting finish with that maintenance.
Some of my projects use a single Lithium cell for power, and the ready availability of low-cost battery protection boards offers opportunity for better projects.
Above, a 1S board rated at 4A and which sells for about A$1 posted in lots of 5.
New and good quality
Use BM112 protection chip + AO8810 MOS tube
The protection board is used to protect the battery overcharge, over discharge, so can’t use as a charger,when you want to charge the battery you need to use the dedicated charger,because the protective board has a time to response to the short circuit, can’t to connect too large instant impact current, such as drills and so on
The main performance parameters:
1. PCB Size: 39 * 4 * 2mm
2. Overcharge protection voltage: 4.2750 ± 25MV
3. Over-discharge protection voltage: 2.88 ± 75MV
4. The overcurrent protection: 4-8A
5. Continue working current: > 4A
Note: Only for the equipment which instant start-up current less than 4A,those starting current instant is great, such as high-current motors, drills, etc., are not suitable for use.
Above are protected battery assemblies based on the board and a 1200mAh LiPo (sells for about A$4) and Panasonic 18650 Li-ion 3400mAh (sells for about A$12). The connectors used are 3A rated JST RCY connectors as used in RC battery applications and readily available with tails for way less than A$1 each set.
The 18650 cell has tags spot welded to the battery contact points, the LiPo has contact tags as supplied.
To use these, the power source needs to supply about 4.5V so as to ensure charging when necessary. The power source needs to be current limited unless you choose to depend on the protection boar’s limit.