Notebook Power Car Adapter 19 Volt

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Car cigarette lighter output DC voltage is 12 V, even when the engine is running will not exceed 13 .8 V, 19 V voltage lower than the normally required of notebook computers. The boost converter voltage conversion, the basic circuit shown in Figure 1, which consists of power switch T, diode D, the energy storage inductor L, and filter capacitor C The inductance constantly charge and discharge, the induced voltage is added to the resulting output voltage on the power supply voltage higher than the voltage provided by the car cigarette lighter.
Diagram Circuit:

(1) S conduction, D, cut-off: the input DC power UIN IIN current pathway formed by the inductance coil L and switch S DC power charging the inductor, the inductance L of the current linear increase in electrical energy to magnetic energy stored in the coil. At this point, the diode D is reverse biased, and output load current IOUT from the energy stored in the capacitor C, as shown in Figure 2 (a) below.

(2) S off: D conduction due to the inductance L of the current can not jump, induced in the coil shown by a very sexy raw voltage. Therefore, the polarity of the induced voltage is left negative right being. The diode D into forward state, the original through the diode D in S during the conduction of the energy stored in the inductor coil to the capacitor C and load RL. C at this stage, the energy charge in the next S period ending provided to the load RL.
The boost converter in the power switch S, one in the state of switch power MOSFET tube. Gate with a series of pulse power tube in the state and off alternately, changing the ratio of off time, you can adjust the size of the output voltage. Suppose that a cycle t, t = tON when the positive pulse, pulse width modulation pulse was sent to the gate of power transistor K conduction; when t = M1 is turned OFF (tOFF), modulation pulse sent to the K tube into the zero volt or negative bias, S in a closed state.

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This is very Simple way to modification standart usb converter to OTG USB.
The most Mini or Micro USB to USB converters are not work if you want to use it for OTG converter, because the 4. pin of the micro usb plug is not connected.

This below is an original cable schematic :

If you want to use it for working OTG adapter you have to connect the micro usb connector 4. pin to GND (5. pin).

Like this below :

This schematic is working me. Let to try this stuff.

Original document USB OTG mechanical

USB RS232 Converter

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USB – RS232 converter, uses only Tx and Rx lines, with selectable 2400, 9600, or 38400bps. PCB projected to fit in old mobilephone cable, most of parts is surface-mounted. For more info see original autor Osamu Tamura site. Pcb’s, driver, and firmware is attached below.

download rs232_usb pcb, schematic, driver, firmware


RS232 to RS485 Converter

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EIA-485 only specifies electrical characteristics of the driver and the receiver. It does not specify or recommend any communications protocol. EIA-485 enables the configuration of inexpensive local networks and multidrop communications links. It offers data transmission speeds of 35 Mbit/s up to 10 m and 100 kbit/s at 1200 m. Since it uses a differential balanced line over twisted pair (like EIA-422), it can span relatively large distances (up to 4,000 feet (1,200 m)). A rule of thumb is that the speed in bit/s multiplied by the length in meters should not exceed 108. Thus a 50 meter cable should not signal faster than 2 Mbit/s.

In contrast to EIA-422, which has a single driver circuit which cannot be switched off, EIA-485 drivers need to be put in transmit mode explicitly by asserting a signal to the driver. This allows EIA-485 to implement linear topologies using only two wires. The equipment located along a set of EIA-485 wires are interchangeably called nodes, stations and devices.

The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, a line or bus, not a star, ring, or multiply connected network. Ideally, the two ends of the cable will have a termination resistor connected across the two wires. Without termination resistors, reflections of fast driver edges can cause multiple data edges that can cause data corruption. Termination resistors also reduce electrical noise sensitivity due to the lower impedance, and bias resistors (see below) are required. The value of each termination resistor should be equal to the cable impedance (typically, 120 ohms for twisted pairs).

Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. But if a star configuration is unavoidable, such as when controlling multiple pan-tilt-zoom video cameras from a central video surveillance hub, special EIA-485 star/hub repeaters are available which bidirectionally listen for data on each span and then retransmit the data onto all other spans.

Download RS232 to RS485 Schematic

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