I saw a series of diagrams on a commercial / ham website explaining to hams how to properly power its products.
Above, an example of their explanatory figures for discussion. The red cross is mine, lest anyone think it is less than confusing and dangerous. Continue reading Hams helping hams
Two bare dimmer modules sold on eBay with identical specification and similar price are compared.
Both claim to have zero hysteresis. Zero
hints a lie!
Hysteresis is caused in simple phase control dimmer circuits at low settings because in each half cycle the trigger capacitor starts at a different voltage depending on whether the diac fired on the previous half cycle.
A serious issue with this snap-on effect is that if power is turned off at low power setting and re-applied, the controller may not switch on.
Above is type 1, a very triac basic phase control circuit. The red capacitor and resistor to its left are snubber components, the yellow capacitor, 4.7kΩ resistor to its left and the 500k pot are the phase delay circuit, the diac is just visible above the red capacitor. Continue reading A comparo of two bare light dimmer modules
The WBT-4000W is a triac dimmer selling for upwards of $25 on eBay.
It claims:
AC 0V-220V continuously adjustable, zero hysteresis, zero latency, superior heat dissipation.
The question is, does it deliver these things? Continue reading WBT-4000W 230V AC dimmer / motor speed controller
This article expands on A flexible test panel for microcontroller based power control projects with some enhancements and accessories.
A LED power meter that I had ordered finally arrived (slow boat from China syndrome).
Above, the upper rail contains a RCD, the power meter which displays Volts, Amps, and kW, or pf, hours, and kWh, a DIN mount terminal block for mains, and a 40A SSR on a heatsink. A clip on CT can be used for oscilloscope observation of mains current. Continue reading A flexible test panel for microcontroller based power control projects – #2
I do a lot of experiments with microcontrollers switching mains powered equipment, and the test beds have always been improvised. It has always been my intention to formalise something for convenience but mainly for better safety.
The article describes a test panel to fill that need.
The panel is constructed on a piece of 3mm aluminium sheet, drilled and tapped to take two sections of 35mm DIN rail for flexible mounting of accessories.
Above is a pic of the test panel in use to test the generic heating / cooling controller (hcctl), a flexible bang-bang controller based on an ATTiny25. Continue reading A flexible test panel for microcontroller based power control projects
The YHDC SCT013 series is very popular for use in energy monitor projects.
Warning, the core is VERY hard, but VERY brittle, don’t hit it with anything hard, don’t grip in with pliers, don’t drop it on a hard surface.
The coil and half core are held in the lower housing by two obvious catches which click over the bobbin. Removal means pulling the assembly upwards gently whilst releasing the catches and feeding cable into the housing. One of the catches will probably catch on the slot in the bobbin, be prepared to release it.
An ideal tool for the purpose is an ordinary $2 DIP chip puller which can be used to get purchase on the two ears on the bobbin that can be seen in this pic. Push a little cable into the housing, pull upwards while releasing the catches, then feed more cable and the assembly is pulled upwards from the housing.
Above is the PCB detail. This one has a TVS (the black component) and no burden resistors. There is a place for two parallel 0806 burden resistors on the board.
The PCB floats on two plastic pin extensions of the bobbin. You may obtain benefit in securing it with two very small fillets of hot melt adhesive as above, small enough so as to not interfere with the guide rails in the enclosure.
So if you wanted to add a burden resistor for 0.333V out at 50mA secondary current, R=0.3333/0.05=6.6667. You could do this with 1% resistors in the E12 value series, 12Ω and 15Ω will give the desired resistance. Likewise for 1V out, 22Ω and 220Ω in parallel will give the desired value of 20Ω.
If you wish to remove existing burden resistors, they can be removed with specialised tooling but small SMD resistors will usually melt the other side solder moments after melting the first side. Position a toothpick with one had to push the resistor sideways, with the other and use the soldering iron to eat one side to melt, move the soldering iron to the other side and push the resistor sideways with the toothpick as soon as both sides melt.
A CT that has no load could develop extreme and damaging voltage within the secondary winding in the presence of primary current. If the CT assembly does not have an integral burden resistor, it is wise to install a TVS or pair of inverse series 9V Zener diodes to prevent excessive voltage lest the external load be disconnected.
The YHDC SCT-010-000 clip-on or non-invasive current transformer is widely used in DIY energy monitor applications, and is readily available on eBay for A$6 including post.
A key issue with current transformers is that current in the primary winding will cause excessive voltages in the secondary winding unless the secondary winding is suitably loaded. The broad rule of thumb is NEVER disconnect the output connections whilst current flows through the primary.
YHDC’s website is typical of Chinese web sites, and I could not find a datasheet for information on the internal circuit and possibly internal protection.
Continue reading SCT-010-000 current transformer protection
On the back of failure to buy decent BN-V11U batteries for my theodolite (Chinese BN-V11U NiMH replacement battery), A fall back was to fabricate a battery that would fit in the battery compartment.
Above is a battery pack made from 5 x 2/3A 1.6Ah NiMH cells. Continue reading Chinese batteries – 5 x 2/3A 1.6Ah NiMH cells
My theodolite uses the once common BN-V11U NiMH camcorder battery.
I purchased a replacement on eBay, they are getting harder to find since changes to regulations about transport of batteries, but there are still quite a few sellers. Continue reading Chinese BN-V11U NiMH replacement battery
This article is a brief review of some issues that were found with initial testing of a Hantek DSO8102E two channel 100MHz hand held oscilloscope.
The DSO8102E is a member of the DSO8000 series (DSO8060, DSO8070E, DSO8100E, DSO8150E, DSO8200E), and shares most specifications across the series.
The specifications are very impressive, and price at just under $1000 for a Chinese brand seemed reasonable (hand held oscilloscopes are expensive compared to bench oscilloscopes).
The test scenario was a practical application, observation of the data traffic to/from a DHT22 temperature and humidity sensor in the project ESP8266 IoT DHT22 temperature and humidity – evolution 2. Continue reading Review of Hantek DSO8102E hand held oscilloscope