View Full Version : help a huge problem

02-05-2010, 01:19 PM
dear everyone,

i have a huge problem using basic stamp.

i am a student who doing a project about using a basic stamp

for my project, i need to design a buck converter using a basic stamp sending the pulse to the transistor
i know the circuit of the buck converter, but i don;t know when i use the transistor for a switch, how can i connect them together and how can i send out the pulse to the basic stamp.

please help me ~
i have searched lots on the net but i can;t find out the solutions

Mike Green
02-05-2010, 01:32 PM
There's no ready-made solution and, because this is a class project, you'll have to solve it yourself.

Have you looked at the "What's a Microcontroller?" tutorial and the "BASIC Stamp Syntax and Reference Manual"? Both of these are downloadable from Parallax's website. Start with the "Resources" tab on the main Parallax webpage.

There are plenty of examples of a Stamp being used to turn on/off a switching transistor to activate a relay or solenoid or LED. Under "Resources", look at the Nuts and Volts Columns index. Column #6 has a nice diagram on the last page.

You'll have to choose a base resistor if you're using a junction transistor. How much base current do you need?

What are the characteristics of the buck converter? Attach a circuit to your next message. Use the Post Reply button and you'll see the Attachment Manager which you can use to upload your schematic (as a PDF or JPG or similar file please). What kind of pulses do you want to have?

02-05-2010, 02:15 PM
i have designed this circuit.

i don;t know it is right or wrong

the program of PWM .

can i write like this?

low 0
pwm 0,127,1
high 0

Mike Green
02-05-2010, 10:37 PM
You're using a junction transistor. What limits the base current? A Stamp can supply 20-25mA. More will damage the I/O pin structure. How would you limit the current?

How is current going to flow from the Stamp pin through the transistor to ground? Transistors are current activated devices. Maybe you should use a circuit simulator to see how your buck regulator will operate. Substitute a pulsed voltage source for the Stamp I/O pin.

Read the description of the PWM statement in the Manual. It may not be what you want because it produces very short pulses that average out to the % on time that you specify. That won't work when you're using an inductor to store energy. It works fine with an RC filter though.

I'll ask again ... What sort of pulses do you need for your circuit? (Repetition rate? Pulse width?)

Some buck regulator references found on a web search:

en.wikipedia.org/wiki/Buck_converter (http://en.wikipedia.org/wiki/Buck_converter)
www.ecircuitcenter.com/Circuits/smps_buck/smps_buck.htm (http://www.ecircuitcenter.com/Circuits/smps_buck/smps_buck.htm)

Post Edited (Mike Green) : 2/5/2010 3:43:46 PM GMT