Design

Julian on February 28th, 2014

Until recently I hadn’t drawn a complete circuit diagram for the PWM5 Solar Charge Controller, just a few sketches of the various circuit elements which are scattered throughout the website. So now here’s the whole thing including doodles and inkblots (click the image for a larger picture). Note that Vbatt appears in two different locations [...]

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Julian on April 15th, 2013

Some solar charge controllers include a load disconnect function. In most cases it just switches off the load when the battery voltage drops below a pre-determined level. Sure it provides the ultimate fail safe against a flat battery, but it’s a crude device. Imagine the scenario: you’re in the shed late at night – it’s [...]

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Julian on April 5th, 2013

I keep coming back to the idea of an MPPT Solar Charge Controller. It would be the maximum power point tracking version of the PWM5. But there’s an idea buzzing around inside my head which I have to research before I can begin the design process. It’s the thought that there might be a coincidence [...]

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Julian on November 20th, 2012

Project Banana is nearing completion. The idea is to make up a kit of connectors to simplify connecting the PWM5 between a solar panel and a battery. On the battery side, there’s a pair of modified crocodile clips which have banana sockets attached. The positive croc clip has two red banana sockets and the negative [...]

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Julian on October 17th, 2012

I’m working on two new charge controller models, the PWM4 and the PWM6. Here is a list of the proposed changes between them and the PWM5. Gumstick Form Factor Both new controllers will be slightly longer but considerably narrower and thinner than the PWM5. They will be similar in size to a 5-stick packet of [...]

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Julian on September 24th, 2012

Spent the weekend working on a new PCB layout for the charge controller which I’m calling Project Gumstick. That’s because the new unit will be about the size of a stick of gum. It’s essentially the same design, with just minor changes to the circuitry and firmware, but making¬†extensive use of surface mount components on [...]

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Julian on September 16th, 2012

Spent the weekend running a new cable from the solar tool shed down to the battery bank. Also built this multi controller panel and mounted it next to the batteries. There are now three separate power feeds from 3 different solar panels that connect to 3 charge controllers. The 3 feeds are also combined through [...]

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Julian on August 31st, 2012

It’s easy to build an intuitive user interface when there’s a keyboard, a mouse, a widescreen monitor and loads of processor power. But what if there’s only one LED for output, and no input device at all? The PWM5 uses a technique where switching the unit off at a particular time (during the initial 2-second [...]

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Julian on August 29th, 2012

I’ve been looking around for a twilight switch (dusk to dawn switch) for 12 volt appliances. It’s a device which closes a switch when the ambient light level falls below a certain level – ideal for turning on a light when it gets dark. There are very few available, and none of them does exactly [...]

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