Hi, this is Wayne again with a topic “Projects With Ryan Slaugh: Useful Circuits”.
You can use a microprocessor, such as the one found in the arduino to do a lot of things, but sometimes i like to create a circuit outside of the microprocessor that’ll. Do some simple tasks for me in this article, i’m going to show you two or three of my favorite circuits that i use in conjunction with microprocessors to use the first circuit you’ll need to have some discrete component circuits, for instance, this is a voltage divider. This is very handy when i need to take a main voltage like 9 volts and create a different voltage out between the resistors, the mathematical formula. There will show you how to calculate what the voltage between the resistors will be given the independent values.
This is extremely handy when i need to take, in this case nine volts to four and a half volts between the resistors or when i need to take a five volt device and interface it with a 3.3 input, such as on the raspberry pi. A second handy circuit is a capacitor charging circuit. In this case, we charge capacitor c2 up to 9 volts through r1, the resistor the time it takes to charge that capacitor is determined by t which is equal to the value of r1 1k times the value of c2 multiplied, those together and then multiplied by 5 Gives you the entire time it should take to charge that capacitor up to the final voltage we see here when we apply the power to the circuit? It takes roughly five seconds for the capacitor to charge to full voltage.
The first circuit we’ll apply these circuits. To is using them with the 555 timer. The 555 timer is extremely versatile and useful tool in a little ic package that runs in two different modes, one is monostable or single shot.
It’Ll, give you one pulse, given a certain input or a stable, which means it’ll. Give you a string of pulses depending on how you wire it up in the case here we’re actually looking at a one shot. When the input on level on pin two goes low, it will give us an output pulse.
The pulse width will actually be determined by r1 and c1. In fact, just multiplying r1 times c1 will give us the pulse width out for this circuit. One of the possible applications for this circuit is using a timed output response to a certain input.
If you need to control a relay to close for a certain amount of time when an input occurs, we can quickly put this circuit together on our breadboard, with the 555 timer, the needed resistors and capacitors wire everything else in apply power and look at our scope. Output whenever the trigger goes low, we get our desired pulse width. On many of my projects, i need a square wave to act as a clock for a different circuit, whether it be a flip flop or counter.
I can use the arduino pin out, or the beaglebone or raspberry pi pin out to do a pulse width modulation. But if i don’t want to waste that pin just doing that job and don’t want to write the extra code for it, i can use the 555 timer in a stable mode. As in this configuration using these mathematical formulas, you can actually figure your pulse width, which is t1 and your pulse spacing, which is t2, and you can calculate frequency. This gives you a nice steady square, wave output whenever you need it as any time with electronics. I want to hook it up and have fun with it, so i go back to the breadboard put in the proper components with the 555 timer hook up my power rails and my jumper wires as needed. Then i’ll hook up my scope to it again. So i can take a look on my scope when i turn on the circuit, give it power. It gives me a steady pulse out.
I can adjust that pulse width on my scope to see and measure just what kind of pulse train i’m receiving operating this in a stable mode gives you a lot of different variety on what you can actually do. You can have cascading timers, intervalometers, missing, pulse detectors. Event: failure alarms or if you put some potentiometers in place of the resistors, you can change the frequency on the go. This actually gives you a variable frequency generator for audio projects.
Here’S an example of such a circuit, a voltage-controlled oscillator, which the schematic is included with the notes of the video changing these potentiometers changes, the output frequency of the 555 into the speaker. The frequency of this particular circuit was pretty high, so i didn’t want to play the sound through the speakers for the video, but here’s the pulse train on the oscilloscope. The last circuit i’ll go through actually involves using an op, amp or operational amplifier. There have been textbooks written devoted just to this component. They can be used as amplifiers buffers comparators, adders mixers, subtractors, differentiators integrators.
They are a very versatile ic and one that if you wish to continue deeply into electronics, you really need to learn the circuit. I’M going to pay attention to here is a very simple comparator, as the name might suggest. This device compares two inputs in this case on pin 2. We have the voltage reference and on pin 3, we have the voltage input. If the input voltage goes higher than the reference voltage, then the output of pin 6 turns q1 on, which is a switching transistor, which in turn turns the led on.
So this can be used when comparing two different inputs that you want to give just one input to your microprocessor or even other circuits, to say that a level change has taken place. One thing that could be noted here is the potentiometers, r1 and r2 are actually voltage. Dividers, like we discussed earlier in and of themselves. That’S what a potentiometer is. So as you change the potentiometer setting, you change the voltage level that is given to the reference pin and the input pin.
Once again, we want to play with the breadboard, so we hook the op amp up the two potentiometers, the led and the transistor, and hook everything up with the jumper wires, and we put it into activity as we change the setting on the potentiometers and vref changes Or v-input changes in respect to each other, the led will turn on and off again. This gives you an opportunity to look at two sensor: outputs, compare them and then give your arduino or raspberry pi or beaglebone the proper input to say when a change has occurred. I hope this video has given you the interest in looking deeper into the 555 timer and the op amp there’s a lot that can be done with both of these components and this just scratches the surface. There’S a lot of literature available online and in books and different schematics that will show you different model circuits. Some of the earliest robotics, for instance, use the op-amp comparator as their main brain the mouse kit, the soldering kit that you can get from maker shed. That has a little light chasing mouse. That’S an op-amp comparator that compares the two light levels. So i hope again that this gives you just a little bit of introduction to these components and you go out and find more. Electronics is really a fun way to get into things and just make a lot of cool projects and there’s a lot of little components out there that help. You do some neat things: happy building, .