Comments on: Max756 dc-dc step-up power supply

By: Anton

Anton — Wed, 01 Nov 2006 00:44:40 +0000

Zane,

This type of step-up isn’t well suited for driving a motor.

The circuit doesn’t produce more power, it just alters it a bit, and in fact loses some in the conversion. The Max756 has a maximum output current of just .3A.

If you could find a 5V motor that’d run as expected at that amperage, you’d have to supply about 1.8 amps at 1V to drive the circuit and the motor.

5V * .3A = 1.5 Watts = 1V * 1.5A

Add in the losses of the step-up (guess 80%, won’t be any better than 90) and you’re over 1.8 amps.

In reality the motor will probably draw close to .5A or more, especially when load increases.

By: Zane

Zane — Fri, 27 Oct 2006 23:34:08 +0000

I was wondering if you could configure me a converter to convert roughly around .7 to .9V to 3 or 5V… unfortunately the source is a small fuel cell and I really can’t tell you how much it produces… but if I put a 19.2 ohm motor on the cell the voltage reading reads .76

By: ingr

ingr — Thu, 30 Mar 2006 22:30:12 +0000

i chopped up a rope light to grab the leds out if it….talk about cheap:)

By: Anton

Anton — Sun, 05 Feb 2006 21:21:12 +0000

Here are a couple good links for some info on how DC-DC power supplies work.

http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-DC/converter.shtm
http://en.wikipedia.org/wiki/DC_to_DC_converter

By: Anton

Anton — Sun, 05 Feb 2006 21:16:29 +0000

Frequently now it’s just a matter of finding a chip that does most of what you need and looking at the reference circuit in the chip’s documentation.

Most of the components around a chip are used to make inputs conform to the limits. In the case of the dc-dc step up the coil, diode, and capacitors provide some oscilation to drive the switcher.

Converting the schematic to a physical layout is up for interpretation. Unless you’re dealing with high frequencies or current it’s not usually that critical where the components go. I chose the layout I did here because of the parts that I had on hand and the constraints of an AA sized space.

By: Jared

Jared — Sun, 05 Feb 2006 20:43:07 +0000

Ah nevermind I see you have posted up some great links about how to do all this stuff.

By: Jared

Jared — Sun, 05 Feb 2006 20:35:07 +0000

Right on Anton. I mean I am computer Savy and I can Solder just fine. I used to be an Auto Mechanic and did a lot of electrical work. I just don’t understand how to lay out compnents ina sequence to achieve a certain effect. Any tips on how to learn what order to place components in to obtain an effect I am looking for? how about good places to buy excellent components?

By: Anton

Anton — Sat, 04 Feb 2006 16:20:21 +0000

I’ve linked to a good timely getting started article on DIY Live here:
DIY Live - Electronics Tutorial

By: Anton

Anton — Fri, 03 Feb 2006 22:32:19 +0000

Jared,

I don’t have a step by step howto, but if you’re a complete noob I’d recommend starting out with something a little cheaper. There are quite a few electronics DIY projects on the web. I’ll dig up some links later tonight and post an article with them.

Some of these components are sensitive to heat and/or static so they might not be the best beginner project. Some practice learning to solder is a good start. You can also check out RadioShack (just don’t ask for help, they’re clueless). They used to have a small book of projects for the 555 timer that wouldn’t be a bad starting point.

By: Jared

Jared — Fri, 03 Feb 2006 21:36:32 +0000

Hey I am a compleate hardware building noob. I have never built a circuit before but I am super interested in this project. Do you have a step by step tutorial on how someone like me can build this?