IC 7815 | Electronic Project Circuits

Posts Tagged ‘IC 7815’

12V input, 12V battery charger by 555,7815

The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors
connected as emitter followers, which in turn drive the voltage doubler proper. The doubler has power resistors built in, which limit the charging current.

BUY Lead Acid Battery Charger Electronic Module

The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit. The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so don’t leave this charger permanently connected to a battery. If you would like to do just that, then add a second diode in series with D3!

There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA.

Source:http://ludens.cl/Electron/12Vcharger/12Vcharger.html
Thank you.

Be the first to comment - What do you think? Posted by admin - January 30, 2008 at 9:48 am

Categories: Battery charger, Converter Circuit Tags: Converter Circuit, IC 7815, lead acid battery charger, low drop out regulator

Check the milli-Ampere-hour capacitance of your rechargeable NiCad batteries

Introduction

With this mAh meter you can check the mAh capacitance of your NiCad or NiMH rechargeable batteries

Normally the cheaper NiCad AA-type cells have a capacitance of 500-750mAh (NiCAD) the more expensive
NiMH AA-cells types are up to 1800mAh.

I built this circuit because the capacitance of some of my older NiCad batteries seemed to be quite low, now I can
check their capacitance. It is also nice to check if the new cells meet the specified capacitance!

Circuit description

IC1/TR1 builds a constant current sink which will discharge the battery with a constant current of 500mA.
IC1 must be a so-called rail-to-rail opamp like CA3140 of Intersil; a 741 will not work here!
TR1 can be any big- low ohmic mosfet. (The BUK455 in the schematic is 100mohm).
The current “sink” must be adjusted to 500mA with P1; TR1 must be put on a small heat sink.

IC2 checks the battery voltage; when it is too low the output (pin 7) will become high. The trip level can be adjusted by
P2; I set the level on 800mV. The value is not very critical because the voltage of a NiCAD cell drops very quickly
when it is almost empty.

IC3 is a pulse generator. It will generate pulses as long as the battery voltage is higher than the trip level of comparator IC2.
When the battery is discharged, MR (master reset) of IC3 will be high and the IC will quit generating pulses.
The pulse frequency is set by P3; the frequency must be set at 500 pulses per hour; with this setting the counter will display
the capacitance in mAh.

The network of diodes resistors and capacitors around Q2 creates a 200ms pulse for the 24V-electro-mechanical 4-digit counter
which is connected to the “counter” terminals.
D4 protects Q2 against the high voltage spikes from the counter magnetic coil.
The LED will blink at a fast rate when the counter is running

mAh meter schematic:

Circuit adjustment & application

* First set all potentiometers in the center position, then switch on the power.
* Connect a power supply set at about 5V to the battery terminals, the LED starts blinking.
* Adjust the discharge current to 500 mA using P1.
* Adjust the cuter frequency to 500 pulses/hour (25 pulses/ 3 minutes) with P3; it will take some time
to do this accurately!
* Reduce the power supply voltage to 800mV and set the trip level with P2 (use the blinking LED as indicator)

Now the circuit is ready for use: when you insert a freshly charged battery, the LED will start blinking and the counter
will start counting. After some time (1-3 hours) the battery is discharged ad the counter will stop. The readout of the counter
indicates the capacitance of the battery in mAh

When you use a different current setting the pulse frequency must be changed accordingly.
The circuit can also be used to check other batteries ;you will have to change the trip level and current sink setting to the
size and the voltage of the battery.

Note that the current sink remains active when the trip level is reached. This is not a problem for NiCAD / NiMH cells,
but lead based batteries (car batteries) can be ruined when they are discharged too deep !
To prevent this you can put about 10 power diodes in series with the car battery, this way the voltage will always remain above 6-8 Volts.
Source : http://www.geocities.com/tjacodesign/mah/mah.html

Be the first to comment - What do you think? Posted by admin - August 29, 2007 at 11:24 pm

Categories: Battery charger Tags: CA3130 op-amp circuits, IC 4060, IC 7815, nicad battery charger

Power supply regulator +15V -15V 1A by IC 7815 & 7915

When I builds the circuit Pre tone control by IC LF353 the finished , but can not be usable. Because of it wants a power supply +15V GND -15V at 500mA current. I pairs then builds the group Dual DC power Supply +15V,GND,-15V. By use pillar equipment be IC 7815 , for +15V and IC 7915 for -15V. Which IC the bilateral can give currrent get about 1A. Other detail both of the circuit and model PCB you can see to follow a image. The transformer should have a primary rating of 240/220 volts for europe, or 120 volts for North America. The centre tapped secondary coil should be rated about 18 volts at 1 amp or higher, allowing for losses in the regulator. An application for this type of circuit would be for a small regulated bench power supply.

Circuit power supply regulator +15V -15V 1A by IC 7815 & 7915