Various diagram: cost

Saturday, November 8, 2014

Low Cost Universal Battery Charger Schematic

Here is the circuit diagram of a low cost universal charger for NiCD - NiMH batteries. This circuit is Ideal for car use. It has ability to transform a mains adapter in to a charger . This one can be used to charge cellular phone, toys, portables, video batteries, MP3 players, ... and has selectable charge current. An LED is located in circuit to indicate charging. Can be built on a general purpose PCB or a veroboard. I hope you really like it.

Picture of the circuit:

A Low Cost Universal Charger Circuit Schematic

Circuit diagram:

A Low Cost Universal Charger Circuit Diagram

Parts:

R1 = 120R-0...5W
R2 = See Diagram
C1 = 220uF-35V
D1 = 1N4007
D2 = 3mm. LED
Q1 = BD135
J1 = DC Input Socket

Specifications:

Ideal for in car use.
LED charge indication.
Selectable charge current.
Charges Ni Cd or NiMH batteries.
Transforms a mains adapter into a charger.
Charge cellular phone, toys, portables, video batteries …

Features:

LED function indication.
Power supply polarity protected.
Supply current: same as charge current.
Supply voltage: from 6.5VDC to 21VDC (depending on used battery)
Charge current (±20%): 50mA, 100mA, 200mA, 300mA, 400mA. (selectable)

Determining the supply voltage:

This table indicates the minimum and maximum voltages to supply the charger. See supply voltage selection chart below.

Example:

To charge a 6V battery a minimum supply voltage of 12V is needed, the maximum voltage is then 15V.

Voltage selection:

Voltage Selection Chart For Low Cost Universal Battery Charger

Determining the charge current:

Before building the circuit, you must determinate how much current will be used to charge the battery or battery pack. It is advisable to charge the battery with a current that is 10 times smaller then the battery capacity, and to charge it for about 15 hours. If you double the charge current , then you can charge the battery in half the time. Charge current selection chart is located in diagram.

Example:

A battery pack of 6V / 1000mAh can be charged with 100mA during 15 hours. If you want to charge faster, then a charge current of 200mA can be used for about 7 hours.

Caution:

The higher charge current, the more critical the charge time must be checked. When faster charging is used, it is advisable to discharge the battery completely before charging. Using a charge current of 1/10 of the capacity will expand the lifetime of the battery. The charge time can easily be doubled without damaging the battery.

Note:

Mount the transistor together with the heatsink on the PCB, bend the leads as necessary. Take care that the metal back of the transistor touches the heatsink. Check that the leads of the transistor do not touch the heatsink.

Thursday, November 6, 2014

Low Cost Power Buzzer

How often on average do you have to call members of your family each day to tell them that dinner is ready, it’s time to leave, and the like? The person you want is usually in a different room, such as the hobby room or bedroom. A powerful buzzer in the room, combined with a push button at the bottom of the stairs or in the kitchen, could be very handy in such situations.

The heart of this circuit is formed by IC1, a TDA2030. This IC has built-in thermal protection, so it’s not likely to quickly give up the ghost. R1 and R2 apply a voltage equal to half the supply voltage to the plus input of the opamp. R3 provides positive feedback. Finally, the combination of C2, R4 and trimmer P12 determines the oscillation frequency of the circuit.

Power Buzzer Circuit Diagram:

The frequency of the tone can also be adjusted using P1. There is no volume control, since you always want to get attention when you press pushbutton S1. Fit the entire circuit where you want to have the pushbutton. The loudspeaker can then be placed in a strategic location, such as in the bedroom or wherever is appropriate. Use speaker cable to connect the loudspeaker. Normal bell wire can cause a signiﬁcant power loss if the loudspeaker is relatively far away. The loudspeaker must be able to handle a continuous power of at least 6 W (with a 20-V supply voltage).

The power quickly drops as the supply voltage decreases (P = Urms 2 / RL). The power supply for this circuit is not particularly critical. However, it must be able to provide sufficient current. A good nominal value is around 400 mA at 20 V. At 4 V, it will be approximately 25 mA. Most likely, you can find a suitable power supply somewhere in your hobby room. Otherwise, you can certainly ﬁnd a low-cost power supply design in our circuits archive that will ﬁll the bill!

Monday, September 22, 2014

500W low cost 12V to 220V inverter circuit and explanation

Using this circuit you can convert the 12V dc in to the 220V Ac. In this circuit 4047 is use to generate the square wave of 50hz and amplify the current and then amplify the voltage by using the step transformer.

author: Ashad Mustufa
e-mail: mustufa66@hotmail.com
web site: http://www.electronics-lab.com

Circuit diagram

How to calculate transformer rating
The basic formula is P=VI and between input output of the transformer we have Power input = Power output
For example if we want a 220W output at 220V then we need 1A at the output. Then at the input we must have at least 18.3V at 12V because: 12V*18.3 = 220v*1
So you have to wind the step up transformer 12v to 220v but input winding must be capable to bear 20A.

Tuesday, September 9, 2014

Low Cost Tone Control Circuit

This cheap tone control schema provides a maximum cut and boost of around 10dB at 10K and 50Hz. Two potensiometer used to control the high frequency (treble) and low frequency (bass).

The first BC109C transistor (left hand side) is acting as a buffer. It provides the schema with a high input impedance, around 250k has a voltage gain of slightly less than unity. As the Baxendall tone control schema is a passive design, all audio frequencies are attenuated. The position of the controls and reactance of the capacitors alters the audio response. The last transistor provides a slight boost of about 3x. The output is designed to feed an amplifier with input impedance of 10k to 250k. Both tone controls should be linear type potentiometers.