Simple Car Battery Charger

Hi there!! i guess this would be my last post perhaps. Have you gone through your car make you sick early in the morning just because you made a big mistake by forgetting to switch off the headlights? Well I've gone through it always. Thus instead of buying new battery, i just made my own simple car battery charger which only use few components. The circuits are shown below.

As simple as it should, it only consist of  two 1N4007 diode, one 2200uF electrolyte capacitor, a transformer and an ammeter.

To charge a battery just connect the + and - terminals of the circuit to the corresponding terminals of the battery.
When the battery is not charged, the ammeter reading shows 1-3 amps.

When the battery is fully charged the ammeter reads Zero  or nearly zero, after which the battery should be removed from the
charger.
The circuit is a full wave rectifier using 2 diodes for rectification. The capacitor is used for smoothing.
I think the circuit works fine without the capacitor since the battery itself acts a BIG capacitor. But when you are using the
circuit to supply 12V (as a battery eliminator) the capacitor needs to be present.
Care should be taken NOT to reverse the + and - terminals while connecting it to the battery.

So if you get it , it is much more cheaper than buying a new battery. That's all from me and singing off.

Dome light dimmer for Cars

Hi there, back to business, previously i have post about some fun electronics on intercom and theft preventer alarm. Before i start today's post, I would like to ask all cars freaks here, what would you like your cars take part in the coolest light decorations? That would probably be a big dream for street homies with V8 under their hood or likely to say some with turbos and superchargers.

Alright that is totally out of the topic! So about doing light decoration on a car instead of a house, this is a simple circuit where you can make your car dome light fade out when you close your car door instead of just goes OFF. This unique circuit makes your dome light look cool.

 

Diagram 1

When a car door is open, the push to off switch of the door is ON and hence it charges the 22 uF capacitor fully

 

Capacitor in white area (edited with Adobe PhotoShop CS3)

The opamp is acting as a voltage follower and its output is same as the voltage across the capacitor, which is 12V when the capacitor is fully charge. Due to high voltage at the output of the IC, the transistor saturates, turning ON the bulb to full brightness.

Now when the door is closed, the door switch is push and so the switch goes OFF. When the switch is OFF, the capacitor starts discharging slowly through VR1 and the 10k resistor and the voltage across it decrease slowly.

 

White highlighted area shows the process (edited with PhotoShop CS3)

Thus at the output of IC 741 also the voltage decreases gradually, hence decreasing the base to the transistor. This produces a slowly decreasing current through the bulb and the bulb fades out and finally when the capacitor is fully discharged, the bulb goes OFF.

After building the circuit, with the push-to-off switch in ON position (not pushed in) i.e. the car door open, adjust the preset VR2 to the required initial brightness of the bulb. Then push the switch in to turn it OFF (or just close the car door) and adjust VR1 for the time to bring the bulb from full brightness to OFF.

I would suggest you set VR1 and VR2 to their maximum values. instead of using the original stock bulb in the car, u can easily replace it with white LED but adjust the maximum brightness in order not to burn the LED as it only consume 1.5V each LED.

Note: 2N3055 power transistor needs proper heat sink

But in my ride I use LED which is slightly brighter than the stock bulb. You even can put these LED's underneath the chair of your car and made it act like a neon.

That is all for today from me. hope you can join the local auto-show in your area. Signing off for today's post just from Mohamad Fairulnizam.

Theft Preventer Alarm

Hi there, this is my second post for today. So before i start posting, I like to ask you, how much stuff have you loss these days? As I am sick of loosing my instant noodle from my locker, i try to fine out a solution from the internet and here it is, I found out how to make a Theft Preventer Alarm. The circuit is very simple like as shown below. This is a very simple circuit using the NE 555 timer IC as an alarm system to prevent the theft of your luggage, burglars breaking into your house, or people start and opening your room door without knocking ( so annoying sometimes). Back to business, this alarm goes ON when a thin wire, usually as thin as a hair is broken. The circuit is straightforward. It uses a 555 IC wired as an astable multivibrator to produce a tone of about 1kHz which gives out a shrill noise to scare away the burglar or eventually make him a little bit more panic.

Edited with Adobe PhotoShop CS3

As shown in the part highlighted diagram above, the wire use to set off the alarm can be made of a thin copper wire like SWG 36 or higher or another option is, you can also even use a single strands of copper from a power cable.


Again like previously, this type of circuit operates on a wide range of voltage from 5v to 15v. So using a 9-volt battery would fit just nice.


That is all from my second post, hope you enjoy it and no more people steeling you stuff of just bum into your room without knocking which might be so annoying for college and universities student nowadays. Here again i am Mohamad Fairulnizam and signing off.

Cheap Intercom System Interface

Hi there, today i like to tell you a little thing about what i have extract from the internet lately. I always wanted to make an intercom system to make people easier to tell who they are before entering my home, so here in is!, I just found out a new solution on making the cheapest ever intercom. Hope that making this intercom will not burden you.



This circuit comprises a 3-stage resistor-capacitor coupled amplifier. when push button S2 is pressed, the amplifier circuit formed around transistors T1 and T2 gets converted into asymmetrical astable multivibrator generating ring signals. These rings signal are amplified by transistor T3 to drive the speaker of earpiece.

This circuit only consume 10 to 15 mA only, so I have no worry about it because I use a 9-volt battery for temporary and after a month later, I replaced those batteries with a 3-pin multi-voltage adapter.

Edited with Adobe PhotoShop CS3

To make a two way intercom, u need two identical unit . Thus of course PC B1 speaker will jump to PC B2 unit and PC B2 speaker will go the other way. Just like I have highlighted in the picture.


That is a little bit from me! Just hope you like it. Coming up soon might be more interesting to you. signing off from Mohamad Fairulnizam