Saturday, August 14, 2010
Mains Voltage and Power Circuits
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 !!
The Success of the LED Lamp
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
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.
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.
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.
Make your own PCB Mechanical Routing/Erosion/Milling Machine at a low cost.
"Design a low cost circuit board milling machine optimized to be mass-produced."
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.
The story and evolution from Behemoth to Microship, water-type HPVs. microship.com. Technomadic goodness.
Surplus Kayaking Books Parts Sensors Nautical Controllers GPS Trackers Geek-free Zone marine electronics.