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1  Using Arduino / Project Guidance / Re: Weather Durable Wiring on: August 13, 2013, 10:20:29 am
thanks dc42,

in addition to those points, will sub-zero temperatures, or the contraction/expansion between temperatures degrade sheathing ?
I was also wondering about condensation on the wires within sheath...

2  Using Arduino / Project Guidance / Re: Weather Durable Wiring on: August 13, 2013, 08:35:26 am
Good Q's !

Conductor arrangement is not finalised as I am trying to make it modular.
In reality, there maybe a 12meter loop with 4 sensors; and 2 spurs with 1-2 sensors each, 1 of 4 meter, the other of 2 meter.
I'll work in parallel where possible.

Current: for each sensor I am expecting .120ma with peak .200ma (no data sheet - working of other user's comments until I can measure for myself)

Arduino location will not significantly add to the distances mentioned above, 0.5m maxmum.

Cable will be routed along a mixture of terrain  : along walls, behind strips of wood; and buried if possible.




From your cable suggestion, I guess I ought to add the complexity of wiring in parallel.
If I have 4 PIRs on a loop, I'll need 4 signal wires + 2 power lines.
Had I been doing this indoors, I'd probably have used 2 power lines on a ring/spur, and 1 ribbon per PIR to send back the signal.
Leaving things open for expansion, I could go with 2 power + 6 signal.

On the other hand, I'm sure this has been done before ... so open to advise.
3  Using Arduino / Project Guidance / Weather Durable Wiring on: August 13, 2013, 06:06:12 am
Hello,

So my next project is a simple pir system to guard my garden/driveway.
The design and construction couldn't be simpler for the most part, but being outdoors all year round in the UK - well that is a new challenge for me.

I have so far, researched various approaches to coating boards/components with coatings, and I'm happy with plans so far.

However, where I am still in the dark, is what connecting wire and terminals to use.
The arduino itself will be indoors, no problem.
But both power lines (5-9v tbc) and signal lines (3.3v) will have to venture outdoors, service 6-12 pir sensors along a perimeter of maybe 12-20 meters.

Being in the UK,temperatures from -26 to +38 (max/min according to Wikipedia) in the shade.
.. so I am thinking basic machine/hookup wire might not last too long.

As far as connections go, where my main wiring loop is spurred for individual PIR sensors, is another dilemma.
I could glue/resin coat connections, making them at least semi-permenant.
Yet I do recall some garden light kit from my childhood.. each light had a connection with 'snake teeth' that bit into the main cable so that you could position/reposition then at will.
I've seen similar on components shops, manly for ribbon cable... but I'm sure these are not weatherproof!
Any suggestions ??


Many Thanks
4  Using Arduino / Programming Questions / Re: AVR Programming Options on: April 08, 2013, 12:04:42 pm
Thanks for the comments and links !

Firstly it's good to have confirmed (with added detail) my thoughts... sometimes you just don't know if you are going in the 'best' direction.

I'll have a better play with this over the next few days but just wanted to leave some feedback for now.

Tbh, I am tempted on reflection, to now opt for the 'official' programmer route, if only because I prefer to have as few 'unknowns' at play at any one time.
This other option I will definitely want to come back to explore as soon as I've mastered the basic.

Thank you for your input smiley







5  Using Arduino / Programming Questions / AVR Programming Options on: April 07, 2013, 07:50:44 am
Well I began like all others with just being happy programming my arduino with sketches and watching motors turn.
Life was blissfully easy:)

Then I started looking at programming AVRs directly (ATTinys).

Using ArdinoISP, and a basic circuit, I managed to use my Uno to load some simple sketches onto an ATTiny84 - leap of joy !
But that seems to have limited use.
I need to get my AVRs to use SPI and to have USB communications, and for that, it looked the only option was developing code in AtmelStudio (or similar).
The above assumption being right or wrong, I did find that AS did provide a much more 'familiar' and feature rich environment for coding.

That then is where I am unsure of my strategy.
As I understand it, working from AStudio, I have to utlilise an specific AVR programmer.
Whilst not the cost of the earth (£15 for a pololu, £25 for an Atmel), I do hate spending where it's not needed, cluttering my drawers, and maybe mostly, underutilizing my existing arduinos.

So, the question (at last !)... can I use Arduino as an AVR Programmer from AtmelStudio to load C and/or assembly, including AS's fuse setting and other features ?
i.e as a direct replacement for an AVR programmer ?

I have treid Googling this, but as soon as you put 'Arduino' and 'AVR' together, you mainly get artcicles about loading Sketches to an AVR via the Arduino IDE.

Any guidance/corrections most appreciated smiley

Thank you

6  Using Arduino / Sensors / CMPS10 - "Tilt Compensated" ??? on: March 12, 2013, 07:58:53 pm
I guess the question is one of those where you think : "is it me, or ... ?"

So I have this unit mounted on my bot.
My mistake first, not have fully realised that an accuracy rating of 0.5% means that I can get reading of 113.2 - 116.8 degress when bearing is truley 115 !

But there is a biger problem looming.

If I tilt the unit say, 10 or 20 degrees; my readings are wild, e.g. 80 - 140 degrees !
I waited a full few seconds for the infernal thing to refresh itself and give me a new 'compensated' reading but to no avail.
This is going to be a major problem if my bot is on rough terrain.

The spec says :
Quote
Accuracy - Tilted to +/- 60 degrees, typically 1%

That means that at 115 degree bearing, my readings should be 111.4 - 118.6  ?

Have I misinterpreted the term 'tilt compensated' ?
Or the term 'typically' ?
Has anyone else had better general accuracy with this unit ?


(All Servos and other devices unpowered (apart from my Mega !))
(Compass mounted high, 30cm away from servos, 15cm away from batteries & Arduino)
(No difference if add 4K7 pull-ups).



In the absence of someone pointing out an obvious 'something' that I've done wrong or overlooked ...
... could anyone reccommend a compass unit that gives more reliable/accurate results ?

SPecs: http://www.robot-electronics.co.uk/htm/cmps10doc.htm


7  Using Arduino / General Electronics / Stupid question: Part for distributing power/ground to multiple devices on: March 06, 2013, 09:12:41 pm
Well yes, I feel daft asking this, but you know when you google and google ... and find nothing !

All it is, all that I'm trying to do is deliver power from my batteries to multiple devices.
What's the 'normal' way of doing that ?
At the moment I hacked a small strip of veraboard, soldered on a 8x2 header socket, and soldered across all the pins on each row.
Battery in on the first pair, giving power/grnd out on all the others.

Unfortunately I've and now I've filled up all spaces ... I'm really not looking forward to making another - veraboard is not easy to hack small pieces off without a lot of waste !

Surely there must just be a standard socket for this purpose ?
Just like a header socket but with each row being continuously connected ?

DOn't really want to add a whole breadboard to the bot, and as I say, veraboard is impossible to cut a 12x2 section off without trashing more than I use.


Hope someone knows of the 'name' for waht I am looking for !?

Thanks if you can help !



8  Using Arduino / Motors, Mechanics, and Power / Re: Wire ratings, specs and interpretation (Vibration Motor) on: February 19, 2013, 11:50:25 am
Thanks Michinyon,

So it's just basic Ohms law stuff then !?
..the wire was just any other resistor in a cirucuit.

I just did the calcs and matched your results, which is reassuring, so thanks smiley

Power & Heat are things that still interest me.
I know this is a puny project as far as power goes, but I am trying to do things 'right' because it'll be a good habit to get into before I progress onto more sizeable challenges.

I've seen heat dissipation ratings on elecronic component data sheets, yet very rarely on wire/cable specifications.
In my case, I was considering ribbon cable to power several motors .. and have just found an interesting article which might be of interest to anyone else with my 'problem':
http://www.mosaic-industries.com/embedded-systems/electronic-instrument-design-new-product-development/cables/ribbon-cable-current-rating

Many Thanks again
smiley
9  Using Arduino / Motors, Mechanics, and Power / Wire ratings, specs and interpretation (Vibration Motor) on: February 19, 2013, 07:18:15 am
Hi,

Well, I am looking at operating several of these :
Product: https://catalog.precisionmicrodrives.com/order-parts/product/307-100-9mm-vibration-motor-25mm-type
Data Sheet: https://catalog.precisionmicrodrives.com/order-parts/datasheet/307-100-9mm-vibration-motor-25mm-type

On the face of it, the wire gauge required is simple.
Typical Op Current : 130mA
Max Operating Current: 160m
Max.Start Current 430mA
And the manufacturer has already attached some lead wires:
Lead Wire Gauge: 32AWG

.. and if I look up the rating for 32AWG, I see 2 values:
1 for 'chassis wiring' and 1 for 'power transmission'.
For 32AWG they are 0.53A and 0.091A respectively.
http://www.powerstream.com/Wire_Size.htm

I did google these two terms (chassis vs power), but "Unfortunately the ship is not a simple one, it depends on a number of factors... "
and seems each individual application is , well , individual !

I did grasp that a lot of it comes down to wire length. .. the longer the wire, the more 'strict' one had to be in adhering to rules.
Given that the supplied lead wires are only 46mm, this how we get away with 32AWG ?

But I will need wires <=1 meter.
I will also not be in control of how frequently the motors will be switched on/off.
Theoretically they will be absolutely hammered, starting & stopping from standstill all the time.
(When 'on', they will be controlled via PWM, but I believe this will induce less than Start Current, as there is already momentum in the unit)

What's worrying me, is that if I need a higher AWG wire, I am going to have to open the motor unit to access the existing lead wire solder points smiley-sad
Or possibly I could use 22AWG (0.9A Power) for 1 meter and simply connect the 46mm leads to the ends ... though seems messy/untidy.

Would anyone be able & willing to advise me on how to approach this problem/calculation ?

I have emailed the manufacturer, but I would appreciate an 'outside' persepective as well ... also might be interesting reading for others on the forums.

Many Thanks
Simon
 

Other notes:
These motors will be mouted on or close to human skin, hence I am quite keen to build in the most sensible margin of error when it comes to safety smiley
10  Using Arduino / LEDs and Multiplexing / Re: Maths Guru ? or of course, a simpler approach in the first place ! on: February 16, 2013, 01:45:29 pm
Chagrin,
I cannot thank you enough.
Pointing me in the right direction is the most perfect answer, and so much better than just handing me the answer on a plate.
At least I will finish this with some new learning and some self respect now smiley-wink

Funny, now you've opened this door to me, this reminds me of 'ray casting' which is something long lost in the midsts of my ever depleating memory.
I shall dig into this with excitement !!

Again, thank you smiley


11  Using Arduino / LEDs and Multiplexing / Maths Guru ? or of course, a simpler approach in the first place ! on: February 16, 2013, 01:03:31 pm
For 'the challenge' , I set out to control multiple 'devices' via Shift Registers.
I wanted to see if I could control each device with PWM throught the SRs.
And yes, I could smiley

However, my approach does have limitations.
I have an array that holds a 'power' value each device.
Then ...

 loop() {
  if(power_value_of_the_bit < counter){turn bit off}
  counter++
 if (counter>limit){counter=0}
}

...and indeed, this works well so far with power levels 0-50, 2SRs & 8 'devices'.

Problem is, for a power level of 25 out of 50, I am actually sending 25 ONs, followed by 25 OFFs.
That delay (25 continuous OFFs), is now limiting how expandable the system will go.
e.g. if I want 100 power levels, or control other devices that require/benefit from more constant signals.
The ideal situation would to alternate, ON then OFF, 25 times.

I thought I had this sorted, until I did the maths.
(I'll use power values up to 100 now to make reading easier)
Power 80, would mean turning the bit off on iteration every 5. [100/(100-80)=5]
And that is very doable by looking at when the iteration counter is exaclty divisible by 5.
But then when we look at a power of 60, I need to turn bits off every 2.5 iterations !

Well I sat with Excel for hours, trying to work out the maths of how to add in the adjustments ... then smoke started coming out of my ears and setting the smoke alarms off!
I MUST be missing something obvious here ?
Or am I asking too much of this type of setup ?

I'd be grateful of any maths insight, or strategy hints, that might help me get a little futher, or indeed - - tell me 'no' !

Many Thanks
smiley

Notes:
> Happy to post actual code if required, but atm I am seeing this as more of an 'academic' question than literal.
> 'Devices' : yes atm they are LEDs, but it is the technique of mastering Shift Registers/PWM that is the real focus here. (LEDs are just easy to use for testing.)


12  Using Arduino / General Electronics / Re: Shift Register Power (74HC595N) on: February 13, 2013, 06:32:50 am
Hi Nick and thanks ...

Do you know of any circuit wizardry that I can employ to safeguard myself?

I am thinking, if my LEDs are in the future powered by external power,
and that power runs out (battery) or otherwise dies ..
... then my Arduino will be hit by a demand way in excess of it's capabilities.

Thanks
13  Using Arduino / General Electronics / Shift Register Power (74HC595N) on: February 13, 2013, 06:14:35 am
I am sure that I'm about to display a gross lack of understanding, but here we go ...

Standard exercise posted all over the internet; 2*Shift Registers, 16 LEDS.
Power supplied to Vcc Pin from Arduino USB 5v Pin.
I had some of the LEDs dimmed, so total current was around 80mA.

All works well smiley

However, in between tests, to save my eyes, I disconnected the wires to the arduino 5v, and the ground.
Yet my LEDs stayed illuminated !?!?
Ok, so they lost some brightness, but well lit all the same.
I had been under the assumption, that the Vcc-5v wire was providing the power for this exercise !?

The only other lines connected to my Uno:
Clock = 4
Latch = 3
Data = 2
OE = 5

Pulling each of these out in turn, reduced the brightness of the LEDs, but no individual wire kills power completely.
I tested the current going through each with the 5v connected & disconnected.
When 5v is disconnected, Latch goes from 0mA to 20mA.
So this is where 'most' of the power is coming from when 5v is not available.

However, even then..
The others get a draw of around 1-2 mA when 5v is disconnected.

Can anyone explain what is going on ?
Is this 'expected' or am I doing something stupid ?
Is my Arduino in danger of getting fried, if I start running 100 LEDs and then disconnect 5v ?

Many Thanks....
14  Using Arduino / Networking, Protocols, and Devices / Re: Snchronyzing Clocks : Communicating between machines ... on: February 08, 2013, 04:34:04 pm
Ahh ... so I think I need to apologize to the previous posters too .. the penny drops now.

So because the baud rate is the slowest part of the process, the code loop cannot execute any faster than the baud rate ?

I do feel so stupid now .. obvious now I think about it.

Thank you for your patience - can we put it down to a long day ?

smiley-wink

15  Using Arduino / Networking, Protocols, and Devices / Re: Snchronyzing Clocks : Communicating between machines ... on: February 08, 2013, 10:42:47 am
Ok,

Thanks for the replies ... but they also make me think that I have not explained my issue clearly enough.

It is not the individual transmissions that I am concerned with.
I am happy with the individual act of a device writing to serial/rf  at a baud rate, and another device  reading the bytes at the same speed.

It is how often these transmissions are sent.

I'll try explain this way ....

Begin Loop
   Send Bytes       // Host  Code
   Receive Bytes   // Client Code
End loop

If I the transmitting host is at 64MHz, and the receiving client is running at 32Mhz,
then 200 bytes will be sent out, and only 100 read in the same time period.

As far as I know, this it to do with processor/controller clock speeds and how fast lines of code are executed.
.... and not baud rate of the individual transmissions.



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