Hobby Projects - Insulation tester, LED Circuits, Meters.

Saturday, August 14, 2010

Mains Adapter 230V AC 50 Hz to Rectified DC

Mains Adapter Converts 230V AC 50 Hz to Rectified DC which replaces a Battery Pack. It was also called Battery Eliminator by older generations as it was used to save Battery Cost in AM Radios.

Mains Voltage and Power Circuits

Mains Adapter 230V AC 50 Hz to Rectified DC

The most important product safety aspect is the transformer, may it be well isolated, may it use a split bobbin, may it have a visible insulation between primary and secondary. May the thin primary wires not slip into the secondary .. when not using split core. Use a Layer to layer insulation for better safety. Use a nice laminated thin sheet alloy core stack, then no hum and no heat. vacuum impregnate magnetics. May the customer be safe and sound.

Power Electronics & Solar Energy

Remember only if we keep a customer alive, he will buy more products. From medicines to transport, from bread to gadgets. The customer is the most valuable asset. If he is kept Alive and Healthy and in a Cheerful mood … He will Buy !!

Torch or Flashlight Circuit Improvements

I fixed a China Torch with New LEDs and a Diode, it failed probably on a drop shock, the battery wire cut … then when put on charge Few LEDs went bad, as battery was absent in ckt.

The Success of the LED Lamp

Torch or Flashlight Circuit Improvements

design review - 1.5uF voltage rating can increase like 440V AC. A current source with low dropout voltage would be great but it builds the cost. The wiring has to be robust. A diode added to keep LED current within some limits on battery overcharge.

LED Lighting - The Future is Here

These type of Torches and Lanterns should not be Turned on when charging. This may blow the LED Array. As long as the LEDs have a constant current flowing through them they are safe. It could be anywhere between 10mA to nearly 25mA depending on the type. LED Arrays can be in parallel or series or a combination of both. The datasheet has to be studied for the high current types.

Never subject these LEDs to a Reverse Bias voltage that is very high. It means reverse polarity. Never allow the current to go so high that it overheats the device, reduces longevity or even damages instantly at high current. These devices survive short pulses of high current. Hence PWM is a way to protect devices and arrays too.

Friday, August 13, 2010

Emergency Light with Fluorescent Tubes

Emergency Light for Portable Use. Note Charger and Battery not Shown. Design from Ludens
12 Volt fluorescent lamp drivers: Three schematics of 12 V drivers for 2, 8 and 20 Watt, plus a lot of explanations about fluorescent tubes. Use the drivers for camping, emergency, boating, etc.

Emergency Light with Fluorescent Tubes

Improper Design of Magnetics or Testing at low voltages can damage the switching NPN. The NPN must have fast switching time, see towers for Cob in pF and .fT in MHz. This may Oscillate for 100 kHz so it has to switch fast, then less heating and better beta at high freq. Choose such a NPN.
The Ic or max current of the NPN can be few times above the current consumption you have planned with the gadget. As a thumb rule if this is a 10W at 10V that means 1 Amp current. Hence choose a device 5 times above 1 A. Use a 5 A device or a 7 A for reliability.

The voltage selection of NPN must also take into account the transients in the switching. If its a sine oscillator like above, the transients, spikes are mild but in square wave switching, the spikes can be very sharp on resonance. These low energy zaps can weaken the NPN and deteriorate its switching and cause heating and eventual failure. So many CFL lamps and Emergency Light's fail quickly as they are not built robustly.

Even this circuit above is good only if is built very carefully.

Mains Powered China Emergency Bulb

A typical Mains Powered China Lamp. On power down, LED light turns on for around 1/2 hr. Gets damaged on lightning activity and wide (uS not nS) transients above 300V. Drawing may have error.

Mains Powered China Emergency Bulb

Many products and components were made over the last 10 years with less regard to voltage and current ratings and product safety.

The circuit design is not everything, engineering the product for reliability, usability and safety is very important. This Schoodle is like a Satire to emphasize the responsibility of electronic manufacturing and engineering.

Two PCB Mills - Jonathan Ward and Ilan Moyer

Make your own PCB Mechanical Routing/Erosion/Milling Machine at a low cost.

PCB Mill - Jonathan Ward - MIT

"Design a low cost circuit board milling machine optimized to be mass-produced."

Low Cost PCB Mill lan Moyer

Low Cost PCB Mill lan Moyer

The overall device has a working area of 4" x 6" with a footprint roughly the size of a letter-sized sheet of paper. Capstan drives were chosen for their simplicity and low cost, and also serve as torque limiters to prevent excessive loads on the small-diameter drive cables.

Nomadic Research Labs and Steve Roberts

The story and evolution from Behemoth to Microship, water-type HPVs. microship.com. Technomadic goodness.

Nomadic Research Labs and Steve Roberts

Online Store for Technomadics

Surplus Kayaking Books Parts Sensors Nautical Controllers GPS Trackers Geek-free Zone marine electronics.