Showing posts with label dc. Show all posts
Showing posts with label dc. Show all posts
Sunday, September 29, 2013
HANDY 0 12V DC POWER SUPPLY ELECTRONIC DIAGRAM
HANDY 0-12V DC POWER SUPPLY ELECTRONIC DIAGRAM
For heat protection, heat sink is needed for the BD679 transistor. It is because it will be over tempered when works more than 200mA.
FEATURES:
0v to 12 volt output:
- 700mA with M 2155
- 1.4amp with M 2156
- 1A with 16v AC 1.5 amp plug pack
Saturday, March 30, 2013
Variable 5 to 20V DC Supply Rise
If you are looking for a low drop voltage regulator that can provide a power supply of 1A with an output voltage of between 5V and 20V DC, National Semiconductor LM2941 Low Dropout Adjustable Regulator is that you can pick to make use of. Its a typical dropout voltage of 0.5V which means that the input supply need only must be 0.5V DC over the desired output voltage. Its other features include internal short circuit current limit and reverse battery protection.
As shown in the schematic below, the regulator has five pins which consists of the ON/OFF control, Input Voltage, Output Voltage, Ground & Adjustable pins. ON/OFF is used for the purpose of switching on & off of the regulator. The capacitors C1 & E1 are to be placed as close as feasible to the regulator.
The output of the circuit can be varied by varying the worth of potentiometer VR1 from 5V DC to 20V DC. The input voltage is limited from five.5V DC to 30V DC. Resistor R1 must be greater than 1K. The worth of the VR1 that needs to be set is calculated from the formula given below:
If R1=1K, Vout = 5V, VR1 should be set to 2.9K ohm.
If R1=1K, Vout = 20V, VR1 should be set to 14.7K ohm
Monday, March 25, 2013
3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM
3V DC to 5V DC REGULATED POWER SUPPLY ELECTRONIC DIAGRAM
A 5V DC regulated output from 2 cells 3V DC batteries. The output current of the circuit is limited to 50mA. However, it still able to supply many microcontroller circuits. 3009 and 560R Resistor provide the 5V DC output, make up a voltage divider network.
Sunday, March 10, 2013
How to Build a Simple PWM Controlled DC to DC Cell Phone Charger Circuit – Science Fair Project
The explained circuit can be easily made at home by any school kid and used for displaying in his science fair exhibition. The circuit is a simple cell phone charger that may be operated in conjunction with any DC source, from a car or a motorcycle battery or from any ordinary 12 V AC DC adapter.
Nowadays we find most of the vehicles have their in built cell phone battery charger units which surely becomes very handy for travelers who mostly remain outdoors travelling in their vehicle.
The proposed cell phone charger circuit is as good as the conventional chargers which come fitted inside the cars and bikes.
Moreover the circuit can be simply integrated to ones own vehicle if the feature is not originally available in the vehicle.
Alternatively one may think of manufacturing the present unit and selling them in the market as an automobile cell phone charger and earn some hard bucks.
Circuit Description
Cell phones as we all know are highly sophisticated gadgets by nature and when it comes to charging cell phones the parameters no doubt also needs to be of very high standards.
The AC/DC cell phone chargers which come with the cell phones are all SMPS based and are extremely good with their outputs and that’s why the cell phone gets so efficiently charged by them.
However if we try to make our own version, it may fail altogether and the cell phones may just not respond to the current and display a “not charging” on the screen.
Cell phone battery cannot just be charged by supplying DC 4 volts, unless the current is optimally dimensioned the charging won’t initiate.
Using voltage regulator IC for making a DC to DC charger, which I myself have discussed in one of my earlier article is a good approach, but the IC tends to become too hot while charging the cell phone battery and therefore requires adequate heatsinking for remaining cool and operative.
This makes the unit a bit bulkier and moreover some significant amount of power is wasted in the form of heat, so the design cannot be considered very efficient.
The present PWM controlled DC to DC cell phone charger circuit is outstanding in its respect because, the involvement of PWM pulses helps to keep the output very suitable to the cell phone circuitry and also the concept involves no heating of the output device, making the entire circuit truly efficient.
Looking at the circuit we find that again the work horse IC 555 comes to our rescue and performs the important function of generating the required PWM pulses.
The input to the circuit is supplied through some standard DC source, ideally from an automobile battery.
The voltage powers the IC which instantly starts generating the PWM pulses and feeds it to the components connected at its output pin #3.
At the output the power transistor is used for switching the DC voltage at its collector directly to the cell phone.
However only the average DC voltage is finally fed to the cell phone due to the presence of the 100uF capacitor, which effectively filters the pulsating current and provides a stable, standard 4 volts to the cell phone.
After the circuit is built, the two pots will need to be optimized perfectly so that a well dimensioned voltage is produced at the output which may be ideally suited for charging the cell phone.
Parts List
R1, R2, R3 = 1K,
P1, P2 = 47K,
C2 = 1n,
C3, C1 = 100uF/25V
IC1 = 555
D1, D2, D3 = 1N4007
T1 = TIP127
T1 = TIP127
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