Sunday, March 08, 2009

PC electrical control box upgrading

Upgrade electrical box

Today, it have finally started. Upgrading the electrical box in my home that control the PCs. It is just to add a new push button on off switches and add in contactors in the circuit.

Why the upgrade?

Since the thing have been installed, the electrical circuit because of high amp startup, has blown off two relays. Both of them are burnt at the contacts. And one day, I was watching it switch on and off, there is a spark on the contacts. And using a clamp meter, it registered a high amp of 5 amp during the instant startup.

Thus, I decided to add in contactor along the circuit to protect the relays. As the relays are to only take in only 5A as stated on the casing, I add in the contactor which can take in a higher current of 25A.


Through the upgrading, the Laptop and wireless supply is also upgrade from normally open circuit to normally closed contact. This is so that after starting up the electrical box, there is no need to press another button to switch on the wireless power. Of course, there is still an option to switch off the current by a push of the button

Hmm…. It is a simple modification, so no need to spend more time on it.

Old System

The old system is to power up by using switches, and after the power is switch on, I have to push a button to startup the power for the wireless, modem, laptop laptop cooling fan. During the startup there is a surge of electrical current when the relay electromagnetic is warming up and pull the contact in micro seconds. During the process, the power created a spark, and cause the contact to melt in very small amount. During the power down, the magnetic de-energise by the parabola curve, and until the stage where the spring takes over and pull the contact away. Over time, the contact melts more and created a weld by itself. And on that day, it would be joined together and cannot be seperate. that is what was observed on two relays that suddenly stopped functioning. I have to dismantle the entire relay, to find the arced material on the contact.

New System

The new system works by contactors, a more powerful type of relay, and it is powered by a more powerful and faster magnetic. It also have a more powerful spring that pull the contact out so that arcing is avoided. And to add to the point, it can withstand 25A, which is 5 times more tolerant than a normal relay.

The new system after the recircuit, void the need for switches. instead, it is operated by another contactor in a single box with the red and green button. The green buttone when pressed, it will power up the contactor, and in turn power the control box. After the rewiring for the laptop power circuit. it automatically switches on by itself without the need to press another button. Thus, All I need to startup everything, is only to press one button to on, and one button to off.

During the poweroff, the current will stay in the push button box contactor so that there is no need to switch off the power supply, and risk being shocked. and also, it saves energy, because there is no standby power. The rest of the buttons remains off. At the same time, also tidy up the wire so that it would be risk-free of electrical shock.


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