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October 22nd, 2015, 11:44 AM   #101
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Why would you want to PWM a motor using 555 timer? Why not just hook it up straight to the battery to get a steady flow?
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October 22nd, 2015, 11:36 PM   #102
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Good question.
The quick answer is that you can change the average volts across the motor, thus controlling the speed.

Now for a slightly longer explanation
When a motor is stationary, there's no back e.m.f. (I will mention this further down), so the current in the motor is equal to the volts applied divided by the winding resistance.
Just to put some numbers on it, let's say the motor windings were 1ohm and you applied 12v to the motor, you'd get a current of 12amps at startup.
As the motor starts to turn and speed up, it acts as a generator and actually produces volts (known as back e.m.f.). Lets assume for the moment that at speed, the motor produces 9v back e.m.f.. The current in the motor is now 3amps (12v - 9v / 1ohm).
By using a 555, we can alter the average volts across the motor, thus reducing the current. This is very useful in reducing the startup current, if you apply 12v across a stationary motor, it will jerk violently as it accelerates fast due to the large current.

Last edited by skipjack; November 6th, 2015 at 11:42 PM.
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October 28th, 2015, 10:06 PM   #103
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I'm struggling with what I should get for my birthday. I want something that will make me technologically more powerful. All I can think of asking for is a stylus for my iPad. Do you guys know of any good ones. I want a fun, cool gadget but I can't think of anything else that has lot of playability. What's hot these days? I want something that will improve who I am and what I do. A device that will expand my universe and technological horizons, making me one step closer to becoming a cyborg.
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October 30th, 2015, 01:00 PM   #104
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Is it more important to know what is going on inside a 555 timer or how it operates in a circuit?
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November 2nd, 2015, 12:27 AM   #105
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It is useful to understand what is going on, if a circuit doesn't work as intended, looking at how the internal parts work can help.
I don't think it's more important to understand the internals of a 555, I use a variety of ICs and don't look at the internals of most them. Usually, the datasheet is enough to make them do what you want.

The pictures on the right are pretty good:
https://en.wikipedia.org/wiki/555_timer_IC
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November 6th, 2015, 09:58 PM   #106
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How do you have fun with servos and motors? Is this really in the realm of electronics? Should I learn Arduino and Raspberry Pi?
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November 7th, 2015, 12:15 AM   #107
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Quote:
Originally Posted by duragrip View Post
Maybe I'm a software guy.
One can make a living out of custom-designed equipment and gadgets. They could be toys, medical equipment, controllers for home electrical items, such as heating systems, washing machines, etc., measuring devices for use in industry, home security devices and numerous other things. Such things are often currently rather primitive, yet tend to be overpriced. However, it helps a lot if you know how to write better software than the software used in existing equipment.
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November 7th, 2015, 12:06 PM   #108
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I want to bring my favorite characters to life: Spider-man's eyes lighting up with sound effect as his Spidey sense goes off (eg. when I get an incoming e-mail on my Apple device). I want my Omega Supreme to be able to lift things with me controlling his movements with servos. Maybe I should stick to more attainable goals?
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November 7th, 2015, 03:53 PM   #109
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How do I apply math to electronics?

I'm having trouble remembering how to set up a 555 timer. I know pin 5 is the Control which is not used so you Cap it to ground. I connect pin 1 to ground and pin 8 to Vcc. After that I start forgetting even though I've watched a lot of YouTube videos. Pin 7 is Discharge so I imagine you connect a Cap to it going to Vcc. Pin 4 is the Reset which is not really used so I connect it to Vcc. Pin 3 is the Output which I connect to an LED in series with a resistor to control the current, or a speaker if I want an audio tone. Where I start really having trouble remembering is how the Trigger and Threshold are worked into the circuit and where to put more resistors. I need some mnemonics to help me understand and recall this stuff.
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November 12th, 2015, 11:11 PM   #110
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Don't worry to much about remembering how to use a 555, this is where datasheets come in very useful. These often have examples to inspire the design of your own circuit.
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