electronics

I've been messing about with a couple of small DC motors and trying to work out how to use one throttle ( speed controller ) to control both motors. I realised that I know next to nothing about about modern electronics. Can anyone recommend a suitable book ? I do know elect. theory and can read a wiring diagram, so don't need basic stuff. Only ones I could find are very basic, very technical or very expensive. As an example ,what's a 555 and what can I do with it? I would like to be able to build something myself, eg speed controller, pulse counter.

I found this on my travels and was impressed... although I know nothing about these things

Another one I found but it was quite expensive, was called Edison5

gl

Edited By Ady1 on 27/02/2014 11:37:14

The best book by far on electronics is 'The Art of Electronics' by Horowitz and Hill. It is not cheap, but covers electronics in a practical sense, and discusses many real world component problems.

The best thing you can do with a 555 is put it in the bin.

Andrew

Hi there, Andrew,

Please explain? What do you have against the ubiquitous 555?

Best regards,

Swarf, Mostly!

A quick internet search for 555 timer will bring up lots of circuits for things like speed controls for small motors, etc.

Those ICs have been around for decades now!

Edited By V8Eng on 27/02/2014 13:33:43

Thanks for the replies so far. This illustrates my problem- The link to the Finnish site is very interesting, I think , But for me might as well be written in Finnish, just can't get it. Jokes about the 555 already, I don't know what one is! May be this time next year I will . I think it may be similar to my computer problems - to much jargon? The experts don't even realise they are using jargon, I'm just as guilty in other fields. Will check out The art of electronics.

A well known auction site has various learn-electronics books on dvd, as well as books

Just been checking out The Art of Electronics, seems about right for me with a bit of referencing, but at the price will have to wait, need a collett chuck first. My 2 motors are 24 V 400 W so will need a bit more oomph ( technical term ) Will try both existing controllers with one pot. and see what happens.

To find out what a 555 is try this, it might be a bit quicker than next year anyway .

**LINK**

Good luck from an expert in absolutely nothing whatsoever!

Edited By V8Eng on 27/02/2014 14:44:13

Gordon: The 555 is a timer integrated circuit. It can be triggered to produce a single pulse, or a continuous train of pulses, the timing of which is determined by an external resistor and capacitor. It was first introduced in the early 70s. Early versions had a number of problems including high supply currents, high current pulses when changing output levels, unexpected double output transitions and wouldn't run at low voltages. Some of these issues have been reduced by newer CMOS (complementary metal oxide semiconductor) versions. It is still widely available, and depending upon manufacturer, can be cheap, a few pence. It has uses in consumer grade electronics where cost is far more important than performance. However, for wider temperature ranges and reliability it has some problems, particularly as the timing parameters are dependent upon external passive components. Given that many devices these days contain a processor, even very cheap devices, that can be used to generate timing pulses that are orders of magnitude more accurate than a 555 timer. It is easier to change software than hardware too! Trawling through my memory there is, or was, a book based on 555 circuits, the publisher might have been Bambini?

Regards,

Andrew

The publisher was Babani.

Mike

The Art of Electronics is an excellent book.

If you want to go bonkers I could recommend books which would be very expensive, and numb your soul.

You would not need them.

I have learned more from semiconductor application notes than ever I did in my studies.

The 555 timer is simply a flip-flop (one bit memory cell) and a window comparator. You can use it in any way you could imagine, but it has a high current output ideal for driving a capacitor. This makes it a good timer. Normally a proper LSTTL non-retriggerable monostable is considered to be a better formal design candidate, but it depends on what you are doing. For the sake of your stock shelf a 555 timer can do more different things.

I've not got one, but I'm pretty sure you could buy a book on just the 555 timer if you wanted.

Speed control on motors is interesting.

It depends very much on the particulars of the motor you are using. If you are using a synchronous motor, then dual speed control from a single control input is easy. If you are using an asynchronous motor then it is not.

If you are using a typical brushless fan motor with an electronic commutator, then you have a means of synchronising the two motors. The commutator requires you to detect the position of the rotor for commutation. Since you have to change the polarity of the magnetic field yourself, when you do you know the rotor angle.

By counting revolutions in time you know the speed of the motor.

You can use potentiometer to specify a speed command signal.

Your commutator design would take an input which controls the current in the winding. The commutator would automatically switch the current polarity every half revolution of the rotor. The commutator would integrate (count) reversals in time. This signal would represent the speed of the motor.

You would then design an error circuit. The error circuit would compute the difference between the potentiometer speed demand, and the reported speed from the commutator. The result of the sum would be amplified greatly and fed into the current command of the commutator.

Obviously if you had two motors, you would have two electronic commutators and two error circuits.

The motors would maintain the same command speed irrespective of the load placed on them individually.

It is important to realise that it would be a "speed match" and not an "angle match".

For an angle match; control over, and feedback from the motor is required at a better precision.

Another, older way of doing this is with a synchro/servo pair. Actually with this scheme a pair of three phase synchronous servo motors can be directly controlled for both speed and angle using a synchro transmitter. All you need is wiring and a three phase power source. The transmitter and the servos, are purely wound rotating components.

These days servos are driven from inverter drives. A typical lathe motor is asynchronous (squirrel cage), but a permanent magnet three phase motor connected to an inverter can be controlled with with speed and angular precision.

Hope that all made sense!

Hi, the book that Andrew metions is IC 555 Projects written by E.A. Parr and published by Bernard Babani (publishing) Ltd. (BP44) It was first published in Feb 1978, it was revised and reprinted on a few occasions, my copy being reprinted in 1788.

My The Art of Electronics is the secound edition and was one of the 1990 reprints and cost me £32.50

Regards Nick.

Edited By Nicholas Farr on 27/02/2014 20:02:49

I think if you were researching a decision to buy Horrowitz and Hill you might want to do a Google for the free online PDF file!!!

Edited By Andy Ash on 27/02/2014 20:12:31

One aspect of electronics overlooked by many is the number of specialized fields within the subject. Depending on specialty people react in different ways to different perceptions. So a small DC brushed motor controller might be an analogue Pulse Width Modulated project to some, a digitally proportioned PWM to a software inclined person and a bridge feedback circuit( using back EMF as a tacho) to analogue types. They will all work but each approach has different strengths and weaknesses.

AofE is a landmark good all round book but the second edition now needs some revision. Where it does work particuarly well is in conveying a "flavour" of good engineering to a very wide subject and in almost completly avoiding heavy maths, they also do what good engineers have always done- they revel in and love their profession.

I would agree with Andrew about the 555 except that I would not be seen dead with a 555 in my bin. By the way the 555 has two comparitors for 1/3 and 2/3 rail thresholds, the three resistors were all 5K ohms in the original which some say is where "555" came from.

Billy,

Hi Gordon

The home tinkering books on Robot building mostly have good discussions and simple practical examples of small DC motor control. I have a few books packed away, else I would give you the titles.

Steve

Hi Gordon,
Some idea about the requirements would help. For example how critical is it that the two motors rotate at exactly the same speed ? This would be important if you are using them to drive two wheels of a car or robot etc as Jason commented. If the application is not critical about speed or position tracking then I see no reason not to use a 555 in a simple PWM speed controller. ( agree with the comments about it not being a very good IC but it would do this sort of thing OK.) If your requirement is critical then you would probably need quadrature encoders on the motors and use a microcontroller. If you do require position tracking then using 2 stepper motors would make the electronics simpler. I cannot help on recommending books on electronics as I just picked it up from electronics magazines from an early age.

Les.