Electronic Speed Controller based on PIC microcontroller

This microcontroller project built by Chris Spurlock. He try to make a cheap electronic speed controller for brushed DC motors. All cost for this project only take about $15 and a little more brain power and programming on PIC microcontroller.

I though it's a suitable project for people that want to make a simple electronic project based on PIC microcontroller. Here is the schematic for the project and For more detail information.

USB Coin/Button Cell Battery Charger

I have designed many small footprint PIC projects (such as, pocket watches and wristwatches) but I cannot make them really portable. To make them portable, I need small power sources. Of course, Coin Cell battery would be the smallest DC source that I can buy. The problem is that a Lithium button cell provides 3 V. which is not enough to drive my projects. I thought about using DC-DC step-up converter to boost 3 V. to 5 V. However, it's a little bit complex to add DC-DC converter to the projects. Moreover, my projects consume a lot of power as they consist of many LEDs, a button battery will not last for a day. So, I stopped my think at that point.

Just recently, I have found a rechargeable coin cell battery at Sparkfun.com. It provides 3.7 V. at 200mAh. I don't know that my projects will work at 3.7 V. or not. But, I want to give it a try. For portability, I want to charge the battery from my computer's USB port. So, I designed a USB coin cell battery + charger breakout board. Like many simple battery charger, I use MAX 1555 as the controller of the charger.

The schematic:




The single sided PCB (40mm x 30mm):


The LED goes off when the battery is fully charged (but the charger is still charging).
Please note that the schematic/PCB are just the design and I haven't made it yet. The parts are ordered and I will update when I complete the hardware.

Multisim Analog Devices Edition 10.0 Free Download

I have found a good and free circuit simulator,Multisim Analog Devices Edition 10.0. As you may know that Multisim is a famous electronics circuit simulation software. It's based on Electronics Workbench from the same company. I have found the free version (not the cracked version) of Multisim by chance and you may not find it on the National Instruments website. It comes with a lot of measurement tools and it's very easy to use. I use it to simulate various analog circuits. The image below shows the screen shot of the simulation of DC-Boost Converter (12V to 150V step up).




Not only analog circuit, but it also simulates digital circuit as one may call it 'Mixed-Mode Simulator'.
Some features and limitations:

• Build simulated component evaluation circuits to quickly assess behavior of over 800 Analog Devices operational amplifiers, switches and voltage references
• Examine the unit under test in the intended circuit topology with up to 25 components
• Use built-in instruments and analyses including oscilloscopes and worst-case analysis
• Swap components easily to pinpoint best design options
• Link to the Analog Devices Design Center for more online evaluation tools
• Instantly access product pages and datasheets of each Analog Devices component
• Upgrade to a full edition of NI Multisim to complete designs and transfer to board layout with NI Ultiboard