PWM is a standard way of controlling analog things with digital electronics. If you need to control lamp intensity, DC motor speed then checks out this video tutorial prepared by Jameco Electronics. PWM can be generated by specialized chips like famous 555 or by the microcontroller.
This tutorial is more for digital guys who usually control things with microcontrollers and other digital circuits. Simple motors, relays, LEDs cannot be connected directly to microcontroller pins because they require more current that I/O can provide and in another hand this isn’t a safe way to do so. Take a look at this excellent video tutorial on how to use the simplest PNP transistor properly when controlling electromagnetic air-valve. Probably you’ve done tons of similar circuits with same relays. What you usually do is connect about 1k resistor the transistor base circuit, and things work just great. But if you want to understand how actually transistor currents depend on each other and how to select proper transistor and right base current limiting resistor spend some time and make things clear. Completing this you will be able to build safer and energy efficient circuits. [via]
No surprise that there are lots of attempts to repeat Arduino success. And this is excellent – more tools more choice – more cool projects. So here it is another excellent open project based on PIC18F microcontroller. It’s a so-called Amicus18. A layout is very similar to Arduino with digital and analog I/O pins, USB interface, and bootloader. Amicus18 based on PIC18F25K20 microcontroller with 32KB flash, 1536 bytes of RAM and is clocked at 64MHz (16 MIPS). Amicus comes along with free Proton BASIC compiler. It requires a Microchip MPASM to be installed. There is a growing number of shields available like prototyping, GPS, GSM, Bluetooth, LCD, Ethernet. .. All you need to get a decent project working naturally. If you prefer PIC microcontrollers and don’t mind BASIC – give it a try. And sure this is an excellent board which can be programmed with your tools and flashed with PICKIT programmer.
Most persistence of vision (POV) projects are very hard to time – questions arise one when to start the sequence of On’s and Off’s to make the pattern of lights. It’s not really that difficult to do the timing but it requires a certain skill and an awful amount of patience. Most of the existing POV units has a synchronizing signal – this may be a opto interrupter, a line sensor or even trip switches switch made out of dangling wires! To make it more sophisticated Rucalgary built a tiny POV with just seven LEDs an ATMEGA48A and a MMA7660 accelerometer from freescale – no he is not advertising its just way too cheap. The accelerometer is used to determine when to start displaying the messages – one more thing that separates this from most POVs is that it has multiple messages stored in an EEPROM – which the microcontroller fetches to display while spinning. He is selling these for to help his college so if anyone wanna help out grab one!
There are quite a lot of digital logic families that differ in their I/O voltage levels. Mainly we use 5V and 3.3V levels in our projects. And there is always a dilemma to communicate 5V with 3.3V devices. In many cases, 3.3V devices come with 5V tolerant pins, but it is better to know than guess. Here is an excellent concentrated chart that provides visual information on how these logic level thresholds differ among technologies. The chart includes CMOS, TTL, mixed TTL/CMOS, ETL, BTL, GT, low voltage glue logic families. FYI most CMOS families are tolerant to 5V input, and probably you won’t, need a logic level converter in many cases. This is OK at a hobby level, but if you are designing end product for marketing then it is better to place a level converter to ensure reliable operation.
Electronics is a precise matter, and you can get caught with stupid mistakes at any time. Probably 99% of faults are yours and left are circumstances. So the most important thing before starting a new project is to read datasheets very carefully. The Circuitguy has written his expertize in power electronics and how to deal with datasheets. Despite the fact, that reading datasheets is a broad topic; here you can find a few great tips on how to study them. As an example, there is an IRFP4568 datasheet taken. So regardless you selection operation mode you must examine carefully key characteristics like thermal, load, etc. And finally, you have to know what you are doing before pressing the “ON” button – especially in power electronics.
THe nothinglabs in his instructable explains how to build the simplest DC motor controller. It supports PWM speed control along with direction and enables control pins. Due to its rugged hardware design, it withstands peak five amps or continuous 2.5 amps without the heatsink. The controller is built by using a couple of TIP120 Darlington transistors, two 220 ohm resistors, and standard 12 relay. It is assembled without the need of PCB – directly on the relay itself. So if you’re looking for the fast solution, this may be a savior.