A Low Cost Hearing Aid Circuit

Small and transportable unit, Useful for previous men and previous women

This most economical, general-purpose electronic hearing help works off 3V DC (2x1.5V battery). The circuit will additionally be simply assembled on a veroboard. For easy assembling and repairs, use an 8-pin DIP IC socket for TDA2822M.

Circuit Diagrams:

 A Low Cost hearing Aid Circuit

Parts:
P1 = 10K
R1 = 2.2K
R2 = 330K
R3 = 680R
R4 = 33R
R5 = 100R
R6 = four.7R
R7 = 4.7R
R8 = 220R
C1 = zero.01uF-10V
C2 = 100nF-63V
C3 = four7uF-10V
C4 = 10uF-10V
C5 = 0.01uF-10V
C6 = 100uF-10V
C7 = 100nF-63V
C8 = 100nF-63V
D1 = Red LED
Q1 = BC547
IC1 = TDA2822M
EP1 = Mono Earphone 32R
SW1 = On-Off Switch

Circuit Operation:

In this circuit, transistor Q1 and related elements kind the audio signal preamplifier for the acoustic signals picked up via the condenser microphone and transformed into corresponding electrical signals. Resistor R5 and capacitor C3 decouple the facility supply of the preamplifier stage. Resistor R1 biases the interior circuit of the low-voltage condenser microphone for correct working. The audio output from the preamplifier stage is fed to the input of the medium-power amplifier circuit by method of capacitor C2 and quantity keep watch over P1.

The medium-power amplifier section is wired round in style audio amplifier IC TDA2822M (not TDA2822). This IC, specially designed for moveable low-power utilitys, is readily available in 8-pin mini DIP bundle. Here the IC is wired in bridge configuration to pressure the 32-ohm general-purpose monophonic earphone. Red LED (D1) point outs the facility status. Resistor R8 restricts the running present of D1. The audio output of this circuit is 10 to 15mW and the quiescent present drain is below 1 mA.

Source : www.electronsforu.com

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Low Cost Universal Battery Charger Schematic

Low cost solution for charging of each NiCd and NiMh batteries

Here is the circuit diagram of a low price universal costr for NiCD - NiMH batteries. This circuit is Ideal for automobile use. It has capability to transform a primes adapter in to a costr . This one can be used to cost mobile phone, toys, moveables, video batteries, MP3 gamers, ... and has selectable cost present. An LED is situated in circuit to indicate charging. Can be built on a basic purpose PCB or a veroboard. I hope you in point of fact love 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 cost current.
• Charges Ni Cd or NiMH batteries.
• Transforms a primarys adapter into a costr.
• Charge cellular phone, toys, transportables, video batteries …

Features:

• LED perform indication.
• Power provide polarity protected.
• Supply current: similar as cost current.
• Supply voltage: from 6.5VDC to 21VDC (depending on used battery)
• Charge present (±20%): 50mA, 100mA, 200mA, 300mA, 400mA. (selectable)

Determining the availability voltage:

This desk indicates the minimum and most voltages to supply the charger. See provide voltage choice chart under.

Example:

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

Voltage choice:

Voltage Selection Chart For Low Cost Universal Battery Charger

Determining the cost current:

Before constructing the circuit, you have to determinate how a lot present will probably be used to charge the battery or battery pack. It is a good suggestion to cost the battery with a present that is 10 occasions smaller then the battery capability, and to charge it for about 15 hours. If you double the charge current , then that you may charge the battery in half of the time. Charge present selection chart is positioned in diagram.

Example:

A battery pack of 6V / 1000mAh will additionally be charged with 100mA during 15 hours. If you need to charge quicker, then a cost present of 200mA can be utilized for approximately 7 hours.

Caution:

The larger cost present, the extra essential the cost time need to be checked. When faster charging is used, you should discharge the battery totally sooner than charging. Using a cost present of 1/10 of the capacity will increase the lifetime of the battery. The cost time can easily be doubled with out damaging the battery.

Note:

• Mount the transistor in conjunction with the heatsink on the PCB, bend the leads as important. Take care that the metal again of the transistor touches the heatsink. Check that the leads of the transistor don't touch the heatsink.

Source : http://www.ecircuitslab.com

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