AndyB
Member
- Location
- Rocky Mountains USA
This is one way to prevent interference affecting servos particularly when they are some distance from the servo driver/controller.
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Hi Andrew.Hello Andy
I know we've discussed this before, a year or to ago, but when you say "some distance" what sort of distance are you thinking of?
Andrew
Hi Andrew,Hello Andy
I know we've discussed this before, a year or to ago, but when you say "some distance" what sort of distance are you thinking of?
Andrew
I've tested all sorts of "fixes" but they do not pass my test. The only thing that really works is the optoisolator.Some of the better servo controllers (MERG) have pull-up resistors built- in as an option plus you can also switch off the signals being sent. If the controllers haven't got pull-up resistors built in, a 10k resistor between positive and signal will help.
AndyHi Andrew,
That depends on how much electrical noise there is in your environment. Radio controlled planes, boats etc are usually a great distance from spark generators which is why servos don't have a problem in those situations.
Model railways usually have lots of things that can produce arcs and long wires and rails that act as antennae to transmit the energy all over the place. There are also the operators who can produce whopping great arcs when they discharge themselves during periods of low humidity Then there might be thermostats and fluorescent lights which are also good arc generators.
I've been able to upset servos just with the cable that comes with them although that's a rather extreme case. Put it this way, if I was selling a piece of equipment that incorporated these servos I would shorten the cable and put the drive electronics no further than a couple of inches from the actual servo.
Many people will tell you they don't have any trouble all. They might say I'm just being an alarmist but they didn't spend years hardening commercial electronic equipment to prevent it producing interference and making it immune to interference from all sorts of sources. There's a lot more to digital electronics than ones and zeros
At the very least I would not extend the cables at all but it's really just a case of whether you are willing to take a chance and hope you don't have any problems or invest more time and energy to ensure you don't have any problems. You could try some tests of course but it can take a lot of time to identify the worst case. Typically that only reveals itself after everything is screwed, glued and bolted down.
If I was in the UK I'd sell optoisolator cards or kits for servos but it would be far too complicated to sell them from here.
Sorry if that doesn't really answer your question but the bottom line is the input to the servo is not designed to operate in electrically noisy environments.
Cheers.
Andy
Andy
Thank you for your very full and clear explanations, speaking as one, who I know you know, has very little clue about electricity let alone electronics, you've done a pretty good job of enlightening me. With cables anywhere from 8" to 24" long between servo and Megapoints control boards, I've understood that this may elicit some unwanted interference.
So my further question to you is "If that was the case, were I to fit one of your box of tricks(circuit) to each servo, might I expect that to solve the problem?". In other words, if the worst comes to worst, can I retrospectively fit a circuit that sorts the problem out?
Last question is what is the large round thing that you say is 17 years old and looks like a mirror?
Kind regards
Andrew
Thanks, Andy, that's good to hear that I can do something retrospectively if needed.Hi Andrew,
Yes, you could certainly see how you get on without any modifications. You might not experience any problems but if you do you could always add the optoisolators later.
The big round thing is a silicon wafer. Each little square thingy is a digital communications chip with many thousands of transistors on it. It's reflective because of the aluminum interconnections between the transistors. The wafer would ultimately be diced up and the individual chips would be encased in a package with metal contacts that you will be familiar with. There was a design error in that particular version of the chip so we had some of the wafers mounted for display purposes.
Cheers,
Andy
I expect I should know what an 8080 is, but somehow I’ve a feeling one could come up and hit me in the face and I wouldn’t know it.
Thanks for the history lesson Martin. Do you mean that all the stuff around 8 bits such as 16, 32 and 64 bit computers, the RAM sizes are all down to Intel's fascination the number eight?
Andrew
Hello TonyHi Martin.
I still think how remarkable it was that the Apollo moon landings were achieved using 4 bit processors and by todays standard miniscul amounts of memory, indeed the development of micro processors was largely driven by the space race during the 1960s.
My first encounter with micro processors was with the 8085 chip set, which was Intel's successor to the 8080 and very similar. I was involved with several projects at work using them. Most of my work was on the hardware side, but I did get involved with the software side later on.
Hi Andrew.
I may regret starting this but...........
There is nothing sacred about counting in 10s (Decimal, base ten). We are so used to it because we have ten digits, i.e.fingers and thumbs, but it is possible to count using any base number. 2 (Binary), 8 (Octal), 16 (Hexadecimal) are the most commonly used as they are all powers of 2.
The basic principle is to count up until the base number is reached and then simply carry one and start counting again. At first the concept takes a while to grasp with our decimal schooled minds, but once the basic principle is mastered, it is not so difficult. I must admit that it was a bit of a revelation when first explained to me many years ago.
Regards
Tony.
Hi AndrewHello Tony
You may indeed regret it because whilst my son is a mathematician and computer programmer, he didn't get those two abilities from me, for sure, as I have some very basic mental blocks about maths that I've never really got over since school. An example being "how can -2 plus -2 = +4". Another is, if I have one of something, and multiply it by zero it then equals zero. To my mind, if I have an apple in my hand multiplying it by zero doesn't magically make it disappear!
Hi Andrew.Hello Tony
You may indeed regret it because whilst my son is a mathematician and computer programmer, he didn't get those two abilities from me, for sure, as I have some very basic mental blocks about maths that I've never really got over since school. An example being "how can -2 plus -2 = +4". Another is, if I have one of something, and multiply it by zero it then equals zero. To my mind, if I have an apple in my hand multiplying it by zero doesn't magically make it disappear!
Kind regards
Andrew
Thanks for the history lesson Martin. Do you mean that all the stuff around 8 bits such as 16, 32 and 64 bit computers, the RAM sizes are all down to Intel's fascination the number eight?
Hi Andrew,
By coincidence, Intel chips are in the news today:
https://www.bbc.co.uk/news/technology-56512430
cheers,
Martin.
A few of us had to learn to work in 12s and 20s when we were younger in the pre-decimalisation days when there 12d to the shilling and 20 shillings to the pound. I couldn't get my head around guineas 1 pound 1 shilling. Also 12 inches to the foot.
Hi Phil.A few of us had to learn to work in 12s and 20s when we were younger in the pre-decimalisation days when there 12d to the shilling and 20 shillings to the pound. I couldn't get my head around guineas 1 pound 1 shilling. Also 12 inches to the foot.
Hello PaulHi Andrew
You sound like a "mathematician" after my own heart, so rest assured you're not alone! My mind also blanks when strange squiggly symbols start appearing accompanied by odd letters, with the word "therefore" as if it's obvious! It's clearly not genetic as neither of my parents are any good at maths, yet my brother has a 1st class honours degree in the subject!
Cheers,
Paul
Hi Andy.I went through all the same metrication steps Tony, and then I had to revert back to Imperial Units when I moved to the US
I only found out recently that a US fluid-ounce is a different quantity from a UK fluid-ounce. It makes it quite tricky to calculate MPG figures for comparison.
Hi Andrew.
You are getting a bit mixed up here. -2 plus -2 = -4. Adding two negative numbers together creates a greater negative number.
Similarly +2 times -2 = -4, however -2 times -2 = +4 as multiplying two negative numbers together cancels the negatives out. Something I haven't had to think about since my college days. Some things just have to be defined the way they are for the system to work, but are as you say, are difficult to comprehend subjectively. For instance you can't physically possess -2 apples.
The concept of 0 is an interesting one as it impiles the abscence of anything and early maths existed without it. It is a basic rule of maths that multiplying anything by 0 is 0 by definition. Applying this to real world objects as you have just done in your example just causes confusion. This was the rational behind the millennium bug with the year 2000 being shortened to 00 by some computer programs, but I couldn't think of any reason why one would want to divide anything by the date, so wasn't suprised when it turned out to be a non-event.
Being a non DCC person, I have not had to deal with CV settings, so can't really comment I'm afraid.
Regards
Tony.
Hello TonyHi Andrew.
Yes, we all have particular strengths (and weaknesses). You are obviously good with percentages, something many people struggle with. Although we are taught a great deal during our education, precious little of it gets used subsequently. Of all the maths I was taught, after addition and subtraction, it is basic trigonometry I use most, although Templot does most of this for us when it comes to the track side of things. Much else is long since forgotten. One qualification I have is using mechanical calculating machines, which rapidly became totally useless of course.
Regards
Tony.
Hi Andrew.Hello Tony
So I suppose my sort of maths is basic and always to do with the tangible, I cant have minus 3 saucepans!
The problem with education I think, is that it's a "one size fits all" approach, bound to fail for a number of us I think and I, to state the obvious, was one of them.
Kind regards
Andrew
It's funny Jim, but when you put it like this (eg ounces, pounds, and stones all being different bases) it seems so much less threatening and mysterious. Suddenly I can relate to it, because its familiar and what I grew up with!I remember doing all the multi-base arithmetic at primary school - Pounds, Shillings (Base 20). Pence (Base 12) was probably the easiest, but Tons, Hundredweights (Base 20), Quarters (Base 4) Stones (Base 8 or 2) Pounds (Base 14) Ounces (Base 16) in addition, subtraction, multiplication and division was probably the worst, or maybe Miles, Furlongs (Base 8), Chains (Base 10), Yards (Base 22), Feet (Base 3) and Inches (Base 12) - all at a pre-teen age. I remember getting fussed about working in Base 2, Base 8, Base 10 and Base 16 when I started working with computers until I remembered what I did as a child.
Jim.
So I suppose my sort of maths is basic and always to do with the tangible, I cant have minus 3 saucepans
Nice of you to say so Tony. What I'm happy to admit to is having had more than my fair share of good luck and particularly in the last 20 years or so, setting out to teach myself or find someone to teach me what I didn't know. Although that in fact, I found that quite hard simply because I often didn't know what I didn't know. That's not meant to sound as glib as it does, but for a number of years, not knowing where to turn, stopped me from developing myself because I didn't know what sort of help to look for or where to find it.Hi Andrew.
You appear to have done well enough in spite of it.
Regards
Tony.
There's me, lacking imagination again Martin. shall try to do better next time!Hi Andrew,
Of course you can -- it means you have 3 customers waiting for a saucepan and none in stock.
If they are waiting to boil an egg, they have my sympathy.
Martin.