'Open'ness Rules!!!

Open source software is mushrooming rapidly. In open source software the software is liberally licensed to grant the right of users to study, change, and improve its design through the availability of its source code. It offers several advantages, though they aren’t very obvious (Its widely discussed in literature). They are free, so no need for licensing issues. Being redistributable, they find greater market penetration. When specific requirements are needed, the source modified by the users to create a variant. This increases the market penetration of the product. The software evolves rapidly and hence sustains in the market for a much longer span than closed software. Also there isn’t any restriction as to stay locked to the same vendor.

With all this, now “open hardware” concept is permeating the planet earth. Like the source code of software, here the (almost) entire hardware design is ‘Open’. The design usually refers to the circuit schematic. It might also include the PCB Layout. With respect to the programmable hardware, design refers to the HDL code (and IP cores) of the design. That pretty much sums it all.

Though they are free, certain licenses are required to exert essential governance. Some are TAPR Open Hardware License, Balloon Open Hardware License, MIT license, GPL etc

Well, if you’ve been thinking that only those petty circuits that you see on magazines are the real Open Hardware, then read along.

No one, except INTEL itself, knows what’s inside PENTIUM Processors. Its closed. But a project by SUN Microsystems, called OpenSPARC is an open-source processor project. The processor is an multicore, multithreaded, 64 bit processor. The block diagram of UltramSPARC T2 a product of the OpenSPARC Project is shown below

“Open Graphics Project” is working on the development of an open architecture and standard for graphics cards. If it makes it big, then that’d be the day when we stop worrying about the whooping costs of GPUs. One of the GPU developed in this project is shown below.

Another interesting open source project, students might be interested in is the SunSPOT. It is an open source hardware and software platform for sensor networks and battery powered, wireless, embedded development. The hardware can be obtained from SUN. Several interesting codes (Java) too can be obtained from SUN. It has wireless interface and several interesting sensors inbuilt in it. There’s also provision to extend the hardware.

To increase the reach of windmills and to assist people in developing countries, ‘Small wind turbines’ has open sourced several windmill kinds.

Robotics was no exception, several robotic designs were open sourced – epuck, RobotCub, OpenRAVE etc. You can see the cute little RobotCub in the pic below

Open hardware has already founds its foundations in variegated fields from simple tools to huge machineries.

Caps, Caps, Caps

Capacitor is one of the most wonderful passive devices invented so far. Its applications have permeated into every nook of circuits. The construction and working of Capacitors are dealt in texts.

Though the concept is as simple as ‘2 conducting plates separated by a dielectric’, several types of capacitors have sprung up.

In college labs, we usually find Electrolytic Capacitors and Ceramic Capacitors.

Why the name? An electrolytic cap uses a conducting liquid(electrolyte) as one of its conducting plate.

Where to use? Typically in low frequency applications, like when you deal with the 50 to 60 Hz signal from power lines. Also, it can handle higher current compared to ceramic caps. Say, you build a 5V power supply for your project, in the rectifier following the transformer, electrolytic caps will be used as filters.

Range: nF to uF

Why the name? Ceramic capacitors are called so because they use ceramic dielectrics.

Where to use? They are used in high frequency applications, unto several megahertz. Amplifiers, oscillator circuits etc are examples.

Range: upto mF

Next is an interesting and advanced cap type called ‘Supercapacitors’ (alias EDLC). They are characterized by their ability to store large amount of charge in a small volume. They have capacitances of several farads. Some have crossed 1000 Farads. These caps store so much charge that they are effectively replacing Batteries in some applications. One highlight feature of these batteries is that they get charged rapidly.

Heard of ‘Capabus’? Electric bus with no permanent connection to power lines. When it stops in a bus stop, it charges its SuperCap, and uses this energy to drive till the next bus stop. Supercaps can be charged in the few seconds for which the bus stays in the bus stop. Do u think batteries could be charged that fast?

Not just bus, even in Formula 1, the KERS (Kinetic Energy Restoration System) introduced in 2009 season, is based on Supercaps to store the energy released during braking, to accelerate later.

It is also used in Regenerative Braking of typical electric vehicles.

Among electrolytic caps, there’s a notable variant called “Tantalum” caps. They have very stable capacitance. Also they offer higher capacitance per unit volume (more compact for a given value of capacitance) and are hence used in miniature applications such as cellular telephones. Eventually they are very expensive.

Is cap an only-AC Device?

So, did you think capacitors find applications only on AC systems, as it does not let DC current to pass through it? Well, caps are everywhere.

One, whenever DC is generated from AC mains, the output is never pure DC (The perfect straight line in the voltage-time curve of DC is hardly seen in reality). So, there comes it – Capacitor Filters to smoothen out the voltage variations in the signal.

Two, EMI/ESD capacitors. At the input lines of the system, even if they are DC lines, EMI/ESD capacitors are used to filter out spurious spikes in input voltage occurring due to EMI/ESD. EMI suppression capacitor is shown below.

You might frequently run into situations where you need 10V from a 5V power source or the like. The obvious solution is voltage doublers or charge pumps. Charge pumps mainly employ capactors. Though they use a clock, it is essentially a DC application.

If you observe a typical DC motor, a capacitor is usually soldered across its terminals. A DC motor generates back emf, and this back emf could damage the circuitry at its output if not handled properly. Providing a capacitor alleviates this problem. (Bypass Capacitor). It is shown below.

Capacitors are momentarily used as DC power supplies in DC circuits, to power microcontroller, to provide smoother voltage drops, handle brownouts etc

Also caps are used in Pulsed Power applications. Steady accumulation of energy followed by its rapid release can result in the delivery of a larger amount of instantaneous power over a shorter period of time (although the total energy is the same). For example, if one joule of energy is stored within a capacitor and then evenly released to a load over one second, the peak power delivered to the load would only be 1 watt. However, if all of the stored energy was released within one microsecond, the peak power would be one megawatt, a million times greater. Examples where pulsed power technology is commonly used include radar, particle accelerators, ultrastrong magnetic fields, fusion research, electromagnetic pulses, and high power pulsed lasers.

And, be cautious. Capacitors, when mishandled, can explode. See below.

Want something more? Heard of Exploding-bridgewire detonator? Its used to detonate a wide range of explosives used in mines and quarries. It has evolved to be adopted in Nuclear weapons. It requires high current surges. To achieve this, high-capacity, high-voltage capacitors with 5 kilovolt and 1 microfarad rating and the peak current ranging between 500 and 1000 amperes are used. It is these devices that trigger the sleeping nuclear bombs to explode. Remember the Fat Man bomb dropped over Nagasaki? It used these detonators. Shown below is the Fat Man bomb and its explosion.

The former explosion was far better, wasn’t it?

Well, we cant argue if the applications mentioned above are DC or AC. But I guess it does give an insight into some flaky applications of capacitors other than conventional fixed frequency AC applications.

"Control" your actuators

If there’s a technical matter on which I’m made to bet upon, then I’d choose, “I bet every student has troubles understanding PWM when he faces it first”. This is mainly because students are not taught the relevance of pwm in everyday applications. Books throw some crazy formlas and hard-to-discern pictures about PWM.

Nevertheless, here we’ll bring you some lucid content.

First, Pulse. A few mistake pulse waveform to square wave form. A square wave varies from +V volts to –V volts. A pulse waveform varies from 0 Volts to +V Volts. There are few more intricate differences too.

What u see below is a simple pulse wave, a train of pulses of equal time period.

The amplitude, frequency and position of the pulse could we varied according to a message signal. This results in Pulse Modulation techniques.

These are ‘communication’ concepts and we are not going to discuss about any of them.

Without much ado, recollect you listening to music in PC. The song that you listen to is not continuous. It has 44000 ON and OFF periods every second (44k is just a rough value to indicate the order of magnitude). But human ear isn’t that sensitive. So we are getting the illusion that its continuous. Similarly, if you could speak such that you have 44000 ON/OFF periods a second, you’d have spent only half your energy in speaking. (Save energy, Save the world). But it just isn’t possible for human vocal chords to respond so fast.

This is the concept in PWM. When you rapidly toggle a bulb switch, it turns ON and OFF. When the switching rate is high that the bulb does not have enough time to turn OFF fully and turn ON again, then it results in a dim glow of the bulb. This switching is accomplished through the pulse train. It turns ON and OFF the device, when it drives the switch (an electronic switch).

Technically, when the ON and OFF periods are same, the amount of power delivered to the device is half the original power. So, the bulb glows with half the intensity. If you want to vary the power, you can vary the duty cycle (the fraction of the time for which the device is ON).

The following figure shows low dutycycle, dutycycle of 50% and high duty cycle waveforms. They’ll correspondingly deliver low, half and higher power to the device.

Now to see where else it applies, imagine a heating device – Iron box for example. Varying the duty cycle varies the temperature/ rate of heating of the iron box.

Consider fan, varying the dutycycle can vary the speed of the fan.

Similar statement holds for the volume of a buzzer and speed of a dc motor.

Present day microcontrollers make it easy to implement PWM in your applications. So, if you’ve got the concept right, then your usage of PWM is bound only by your imaginations.

Weblinks:

http://www.netrino.com/Embedded-Systems/How-To/PWM-Pulse-Width-Modulation

http://en.wikipedia.org/wiki/Pulse-width_modulation

Present, yet absent!!!

When a IT student comes up with an idea/thought, all that he has to do is download a compiler, install and code his program and run. Eureka!!! He has his idea in action. But, when it comes to an electronics engineer, whenever you have thoughts like “what if I add a new resistor here in this amplifier?”, “What if I increase/decrease the value of this component?”, or “what if……?”. Is the only way to learn electronics is to buy boards, components, do extensive soldering and finally measure a voltage on which u had a thought?. Well, things aren’t that worse. You have an answer – Simulators!!!

Simulators are software that imitate real life things, which are here electronic circuits. All you have to do is, install the simulator, draw the circuit you have in mind and run it. Eureka!!! The simulator will tell you pretty much exactly how your circuit will behave in real life. And lucky you are born in this part of the century. Simulators are very user friendly and pretty much easier to learn (compared to the laborious task of physically constructing every circuit Simulators are definitely easier).

I’l brief about 3 simulators that I’ve used.

1)Multisim

2)Orcad

3)Proteus

Multisim: A very good one to get started with. “Very “ Easy. If you’ve used MS Paint before, then you’ll feel ‘at home’ with Multisim. As easy as that. You can find more details of the software at www.ni.com. It has an extensive set of components, virtual instruments, simulation options. Has some digital logic tools too. The interface is very realistic. You can FEEL the electronics with its realistic CRO, Multimeter, 3d components etc. I personally suggest this software for the beginners.

The following figure shows Multisim showing a sample circuit with its simulated output in an real-like-oscilloscope.

Orcad: Now this is a very professional software. It’s a STANDARD. If you are looking for a simulator with very advanced options, allowing in depth configuration facilities and industry standard tools, etc etc etc, then ORCAD should be your choice. The learning curve is a little steep, but its worth it, if you are using it for bigger projects and not just learning basics. Visit www.orcad.com for more details.

The following figure shows a sample of the Orcad interface.

Both the above softwares allow you to do more than just simulation. You can simulate, obtain the output in a presentable form, do post simulation analysis, DESIGN THE PCB, do the pcb routing, get the bill of materials etc.

Proteus: Alright, this is a cool software. Like ‘wicked’ cool. Its not for plain electronics. If you are interested in a microcontroller system, then you can choose Proteus blindly. Offers a huge set of microcontrollers and interface devices like LCDs. Microcontrollers include a wide range, from basic 68000, 808x, 8051 series to recent versions of AVR, ARM and PIC Micrcontrollers. You can build the circuit, write code for the microcontrollers, assemble the code, and see the code in action. Offers good debugging options too. If you love microcontrollers, you’ll love this one too. Visit www.labcenter.co.uk for more details.

Ya. What you see below is real. It’s a chess game programmed into a pic microcontroller programmed and simulated in Proteus. Nice LCD interface isn’t it?

Regarding the computing resource required, Proteus is very light. Multisim is light. Orcad 16+ can be heavy if you intend to do complex simulations. Orcad 10 was light.