Friday, December 21, 2012

12V-24V High-Current Motor Speed Controller Part-3

In first part we discussed about the detail of circuit, back EMF and Mosfet protection; and in second part we covered the display and menu, in this third and last part we will build and test our project. 

The DC Motor Speed Controller is built on two PC boards: a main board, and a display  board. These are joined together via a 12-way flat ribbon cable, which plugs into a pin header on the main board. 

The main board can be assembled first – see Fig.9. Start by checking the PC board for hairline cracks and for any visible shorts across the copper tracks, especially between the ground plane and any adjacent tracks. In addition, check the hole sizes for the larger hardware items by test fitting these parts into position.

Making a link
That done, begin by installing the 17 wire links. These must go in first, since some of them run underneath some components.

To straighten the link wire, first clamp one end in a vice, then stretch it slightly by pulling on the other end with a pair of pliers. It’s then just a matter of cutting the links to length and bending their leads down through 90° to match the holes in the PC board.

Saturday, December 15, 2012

12-24v High Current Motor Speed Controller Part 2

In first part we discussed about the detail of circuit, back EMF and Mosfet protection; in the second part we will cover these:

Other protection measures
As already mentioned, diode D1 provides reverse polarity protection for microcontroller IC1 and the switchmode supply (IC2). Zener diode ZD1 is self-protecting in the case of reverse supply connection. However, if the supply is reversed, there will be a heavy conduction path via fast recovery diode D3 and the internal substrate diodes in the four power MOSFETs. If you are lucky, the 50A fuse will blow before the MOSFETs are damaged, but there is no  guarantee of this. SO dOn’T rEVErSE THE bATTErY cOnnEcTIOnS!

In a similar vein, if the outputs are shorted while power is applied, high current will flow  through the MOSFETs. Again, if you are lucky, the 50A fuse will blow before the MOSFETs go up in smoke. In reality, the 50A fuse is there to stop a fire! SO dOn’T SHOrT THE OUTPUTS TO THE MOTOr.

If the motor is under heavy load and becomes stalled, high currents will flow in its armature.  Depending on the motor’s rating, this may or may not blow the fuse. If the fuse  does not blow during stall conditions of the motor, the MOSFETs should survive, although they may get very hot.

Saturday, December 8, 2012

DIY Desktop-Table LED Lamp

Hi guys lets do something woody!!! something you may wanna do!. If don't then,.... what can i say its your choice.Ok lets get started.
In this DIY i ll tell you the story of my diy wooden desktop and wall led lamp. So first of all the things required are: 1)round slick/rod of one inch dia.
2) Some nuts n bolts 

3) some washer 
4) 24 High bright LEDs 
5) 8 100ohm resistors 
6) 12v adaptor 
7) small piece if MDF board 
8) on/off switch
9) piece of flat thin wood (as you can see in fig bellow, actually i don't know the name of this wood!!! ) 

Thin Wood stick n round wood piece