Switching a circuit from a 2 wire dc motor to 3 wire motor

thanks for checking out my question. I am an extreme newbie (having done software all my life, hardware is making me feel super dumb), and big picture is I am trying to replicate this work: http://words.iame.li/post/112091812552/buttonpusher although he seems to be taking some shortcuts which I don't quite understand (where does the yellow and green wire go on the pi? How does he join the green wire up to the power supply?)

As part of my learning, I decided to do it by steps on an established kit. I have just completed this circuit: https://www.sunfounder.com/forum/superkit-v2---lesson-7--dc-motor?p=2

as you see from that rather complicated chart (which i assume is for protecting the RaspPi) the motor is ultimately powered by two wires, positive and negative.

I now want to take this setup, WHICH WORKS!, and apply it to the Futaba servo which he uses (https://www.amazon.com/Futaba-FUTM0031-S3003-Standard-Servo/dp/B0015H2V72) but simply plugging in my wires to the red and black receptors of the Futaba servo didnt work, presumably because I need a neutral wire to ground the new white wire from the Futaba? I must be sounding so retarded now to you guys, but I appreciate any and all tips as to fundamental concepts i must go and learn and terms and things i need to google. Please help!

Replay

The standard motor they use, and a standard Futaba servo, work in different ways.

A standard permanent magnet DC motor just turns continuously when you apply power to it, speed more or less proportional to voltage, or in the case of PWM, to duty cycle. It's just dumb physics-obeying hardware. The L293 is a power switch, a full H-bridge, which takes the low power logic levels from the Pi, and switches higher currents capable of turning the motor. It can drive +/-, or -/+ to the motor to make it turn in either direction, those wires to the motor are not power supplies or always +ve or -ve. U2 and 3 are opto isolators, for bomb-proof isolation between the Pi and the motor and its power supplies, but not absolutely necessary for function.

A standard servo contains a motor in it somewhere, but has a very different function. It is intended to go to a specific shaft angle within an angular range of about half a turn. It is used for controlling rudder and throttle position on radio controlled models. It contains a gearbox, position sensor, and some comparator and drive electronics. The desired angle of the shaft is encoded in the length of logic pulses sent into the white wire. A 1.5mS pulse is central, 1mS full left, 2mS full right. Typically, pulses are delivered every 20mS or so. In the absence of a pulse, it will hold the last position.

If you want to drive it directly from your Pi, connect red and black supply wires to +5 and gnd respectively. Connect the white wire directly to the one of the GPIOs, or to the output of either U2 or U3 if you want the opto-isolation for safety, or via the 1k resistor (some protection) that your first project uses. Use your software skills to generate a stream of pulses on the GPIO, length 1mS to 2mS, 20mS apart.

I've not looked myself, but I would not be surprised at all if you googled 'pi servo open source', and found stuff ready to run that would put the right sort of pulses onto the GPIO.

The author of the first project was misleading slightly when he said 'the servo spins for a few seconds', because it doesn't, it just changes position (noisily, over a second or so) to push the button.

If you connected red and black from your servo to the output of the 293, I hope it didn't go bang when you applied reverse voltage to it. I would hope that as servos are designed to be supplied by batteries (which can be reversed) and used by youngsters, they would be designed to survive supply reversal.

In software terms, what you're trying to do is plug a USB lead into a 3.5mm audio jack! Both have their standards and levels of complexity, but you're lacking the experience at the moment to anticipate how different.

Category: dc motor Time: 2016-07-30 Views: 0

Related post

  • How to switch separate circuit from doorbell? 2016-06-24

    My doorbell rings as long as somebody pushes the button. I measured 10V AC at the bell when it is ringing. Now I would like to use this AC voltage to switch another circuit. How can I achieve this? Here is what I want to happen when the doorbell butt

  • Switching a circuit from an I/O 2013-11-11

    I have an audio amplifier that draws about 200-300mA max that I would like to switch on/off using either an I/O line or a the switch pin from the headphone connector. I was thinking about using an npn transistor or an N-type FET but I've never really

  • What might be the cause of high pitch sound coming from a switching regulator circuit 2012-06-30

    We designed a switching regulator circuit using a 1.5Mhz, internal-switch, switching regulator (semtech.com/images/datasheet/sc185.pdf). Vin is 5V, Vout is 3V3. We have an input capacitor (47uf), an output capacitor (47uf) and an inductor (1uH). The

  • How do I know whether a circuit (originally for 5 wire) will work for four wire stepper motor? 2013-12-27

    There is a very old and popular instructable 3 axis stepper motor driver, http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/ As clear from the image , it's a six wire motor connected to the circuit. According to me th

  • Powering circuit from 12V with stand-by battery + solar charger 2014-02-11

    I did some research but I haven't been able to find the information that I really want. I am building a home made security system consisting of several IP cameras. Brownouts are very frequent so I have purchased a 12V 7Ah that I am intending to use t

  • What's the difference between virtual circuit switching and circuit switching? 2014-10-26

    Circuit switching's packets take the same route as virtual circuit switching's do. So, how do I distinguish between virtual circuit switching and circuit switching? --------------Solutions------------- In the good old days of cables that consisted of

  • Not understanding a circuit from a book im reading 2014-12-25

    Well Hello and merry xmas! , I got a qeustion of a circuit witch i dont understand (yes its probaly a stupid qeustion but i cant figure it out) So this is the text from the book . Because of the difference in resistances and the relatively high turn-

  • Create circuit from current–voltage characteristic 2012-07-04

    I'm trying to create a circuit from a given current–voltage characteristic like this: I want to use ideal diodes/ideal voltage source/ideal current source So my idea was for the dotted graph the left circuit and for the solid graph the right circuit

  • Protect DC Circuit from too much voltage 2013-03-03

    How do I protect a 3v DC circuit from being damaged if someone accidentally plugs in a 12v power supply? The circuit will draw much less than 1 amp. --------------Solutions------------- One thing not specified by the original question is if they are

  • BJTs versus (MOS)FET to switch a load from a microcontroller 2013-04-17

    I would like to know what are the reasons for choosing bipolar junction transistor (BJT) versus a field-effect transistor (FET) (MOSFET or a JFET) to switch a load from a microcontroller. In our hypothetical situation, assume that the load requires m

  • Small size clamping device to protect 5V circuit from high voltages 2014-08-21

    Are there any small size clamping device or ICs to protect a circuit working on 5V? I would like to protect the circuit from high voltage like 200V - 300V. Edit: I want to use SN6501 or MAX845 to make dc-dc converter. The chip should just stop workin

  • How can I switch multiple circuits using switches with limited pole counts? 2014-10-25

    I am trying to refine the design of an audio switch that I built a while ago. Since this is used to connect two inputs (two sound cards) to five possible outputs (speakers, tv, etc) with stereo audio plugs, I am dealing with three circuits. Since fin

  • Which diode to use on my RC switch debounce circuit? 2014-10-27

    I am choosing parts to build an analog RC switch debounce circuit. I plan to implement the circuit described here: http://www.ganssle.com/debouncing-pt2.htm (see "An RC Debouncer"). These are the other parts I plan to use for the circuit: Voltag

  • Can we use 3.3V voltage divider circuit from 5V voltage regulator for (800ma load and 3.3v)? 2015-09-28

    I am using (lm2576) 5.0v regulator from 12v battery 2-amps for my raspberry pi. I want to use 3 LDR and 5 proximity IR sensor for my mini project. For all sensor I need only 3.3V voltage. It is sufficient to use 3.3V voltage divider circuit from lm25

  • Modelling Circuit from FSM using Verilog 2016-02-07

    I am trying to understand the concept of modeling a circuit from a FSM in Verilog. I have tried to write down the procedure that I have used in the image below just to make sure that I did it right: Based on the solution the circuit is as below: The

  • Are there any issues switching a user from a roaming profile to a local profile? 2010-02-04

    We have a Windows Server 2003 environment with XP Professional laptops. If I switch a user from a roaming profile to a local profile in active directory, by clearing the profile path, will this cause any problems on the laptop the user always uses? (

  • Would switching to InnoDB from MyISAM improve performance of comments table? 2011-01-10

    A site I've built gets lots of comments in a short space of time - so perhaps 100 comments might be left in 5 or 10 minutes. This seems to cause a pretty heavy load on the database, especially when combined with recent comment widgets - I've seen ser

  • T-SQL: How to switch all partitions from one table to another? 2011-10-14

    Is it possible in a single statement to switch ALL partitions from one partitioned table to a staging table? --------------Solutions------------- For anyone wanting a solution to this, here's a sproc I cooked up: -------------------------------------

  • How to disable Switch User option from Fedora 15 2012-03-14

    Is there a way to disable the Switch User option from a locked screen on Fedora 15? I've tried this way, but no luck, since gconf-editor has no effect. --------------Solutions------------- I found 2 ways of doing this. Both involve XScreenSaver. Eith

iOS development

Android development

Python development

JAVA development

Development language

PHP development

Ruby development

search

Front-end development

Database

development tools

Open Platform

Javascript development

.NET development

cloud computing

server

Copyright (C) avrocks.com, All Rights Reserved.

processed in 3.249 (s). 13 q(s)