Chinese CH2 terminal block (CH1 CH3)

I purchased some CH2 terminal blocks on eBay. They were advertised as 250V AC, 10A, to suit 2.5mm^2 conductors.

Above is the seller’s pic of the terminal block.

Features:
– Fast wiring
– Prevents the wire from shorting out
– Free drilling screws, increase the speed of assembly
– Can completely replace electrical tape
– Cost savings
– Fast、efficient and safe
– Widely used in the wire connection,especially for LED Lighting Ceiling
– lamp dedicated wiring clip.

Specification
– Material: PP Flame Retardant Plastic
– Reed material: Manganese Steel Sheet
– Color: White
– Voltage: 220V
– Current: 10A
– Type: 2Pin Connector
– Style:Self-locking Cable Connector
– Temperature: -40 to 150 Degrees Celsius
– Wiring: Wiring Capacity From 0.5-2.5 Square Wire
– Size: CH-2:Approx. 20*17.5*13.5mm

Close inspection cause me concern for their performance, there is no current rating marked. The product is labelled KX-P2 and appears to be a product of Foshan Shunde Kaixiang Electrical Co Ltd, but the Chinese being great copyists, this may have come from another source. Continue reading Chinese CH2 terminal block (CH1 CH3)

Conversion of oyster luminaire to LED

I purchased a kit to convert a oyster luminaire to single colour LED on eBay. The kit was nominally 18W, supplied with the 5730 LED plate and driver module for about $10 incl shipping.

A cautionary note: do not play with these things unless you have the necessary competencies.

The thing was packed in nothing more than a plastic mailing bag and was bent in several places in transit from China. It was not usable in that state and some LEDs were not working so my money was refunded in full (after the usual tug-o-war eventually resolved with eBay intervention). It had to be straightened to be usable, but at the risk of damaging LEDs and possibly cracking or compromising the insulation layer.

Above, after flattening the back plate, nearly half the LEDs are not working. Continue reading Conversion of oyster luminaire to LED

Programming a certain type of Chinese 315/433MHz EV1527 compatible remote relay

This article describes the programming sequences for a common Chinese 315/433MHz remote relay which works with the common EV1527 transmitter.

The EV1527 should not be confused with high security protocols, the transmitter has burned into it four fixed supposedly relatively unique codes (in a space of 1 million code possibilities) and sends the burned in code associated with the transmitter key each time it is operated. This should not be confused with rolling code systems such as KeeLoq. This information is not usually disclosed by sellers.

These are usually supplied with little or no instructions, or bad online translations that are quite misleading. I dare say sellers have refunded money in lots of cases due to user confusion about programming them or compatible transmitters. This information might assist owners to find a working solution.

Above is an example remote relay (~$3 on eBay), they are available with a number of channels and may look physically different but use the same or similar firmware. Note that though the relay on this one is rated at 10A AC, that rating is for resistive load and it is rated at 5A AC for an inductive load (PF=0.4). Continue reading Programming a certain type of Chinese 315/433MHz EV1527 compatible remote relay

Chinese wattmeter / power analyser fix

I bought a little wattmeter / power analyser with SB50 style plugs on it on eBay for about $20.

These devices have been common in the RC market for many years, and I have found them useful for a number of things but note that the input -ve lead is NOT directly connected to the output -ve lead, you cannot use them where the input -ve and output -ve are common.

 

The problems

Above is the promo pic. Of course they are not Anderson plugs, but clones. Continue reading Chinese wattmeter / power analyser fix

Normalised RMS voltage of a full wave phase controlled power waveform

The recent article Soldering iron – temperature control failure gave a plot of V’rms vs conduction angle for a simple full wave phase controlled AC waveform, and I have been asked to explain the derivation.

The phase controlled switch turns on at some delayed time from the zero crossing of the AC waveform, and conducts until the next zero crossing.

With the simplest circuits, there is a practical limit to the achievable stable range of conduction angle, and a minimum of about 50° to a maximum of about 160° is typical.

The RMS voltage is the square root of the mean of the square of the instantaneous voltage. We can write an expression for the normalised RMS voltage as a function of conduction angle θ. Continue reading Normalised RMS voltage of a full wave phase controlled power waveform

Soldering iron – temperature control failure

I wanted to modify a soldering iron to insert brass threaded inserts into holes drilled in plastic parts, and for this application looked to eBay for an inexpensive temperature controlled soldering iron that could be adjusted down to around 200°.

Well first check was of its temperature when set to 200°.

Ouch, that is a fail. The Chinese cheats have supplied product that does not comply with its description. Continue reading Soldering iron – temperature control failure

Hitachi DB3DL2 UC3SFL repair

The UC3SFL charger for my Hitachi DB3DL2 screwdriver departed this world after just 8 years with a bang, several parts around the main switching transistor deposited as soot inside the cover.

Above is a view of the underside of the charger board, it is very complex, lots of parts, and there are lots of parts on the topside. Ouch, this is going to be expensive.

Yes, it is the replacement power supply is more than half the price of complete tool with two batteries (~$200)… so that is not on.

Modification / fix

The screwdriver’s LED control board has already failed (probably a low grade Chinese electrolytic capacitor) and had to be removed as it would switch on spontaneously and flatten the battery. The hole left vacant by the removed push button provides a convenient exit for a charger cable. Continue reading Hitachi DB3DL2 UC3SFL repair

On Thevenin’s theorem – #2

On Thevenin’s theorem looked at a simple source network to demonstrate some key characteristics and limitations of Thevenin’s equivalent circuit.

The example network used was linear in V,I for all V,I combinations possible. Let’s now look at a network that is not linear for all V,I, but is sufficiently linear over a sub range to be usefully modelled using Thevenin’s equivalent circuit.

Black Box for discussion

For the purpose of discussion, we have a Black Box with just two terminals and is a source of DC voltage and current, and the internal implementation is hidden from us.

A series of measurements is made with different load resistors attached and the voltage and current at the terminals is recorded and plotted uniformly stepped currents.

The V,I characteristic is clearly non-linear, but on closer examination there are two fairly linear regions, from 0.008 to 0.060A and 0.08A to 0.1A. It is a device that is usually used in the region below the knee, and for our application, let us concentrate on 0.008 to 0.030A. Continue reading On Thevenin’s theorem – #2