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4621  Using Arduino / Project Guidance / Re: Building a horse feeding machine on: September 20, 2013, 01:40:57 pm
The more of the user interface you can move away from the feeder unit, the better it will be from the technological point of view. Maybe you need to be actually looking at the stable before you can decide what feed adjustments are needed, but I'd still prefer to have a central management PC that has all your configuration and logs in a safe and secure form and can distribute updates to the feeders as needed, rather than store and update them directly. If you want you could provide a web based UI from the central server which would then be accessible via any smartphone etc that you happen to have with you when you visit the feeder.
4622  Using Arduino / Project Guidance / Re: Automation on: September 20, 2013, 01:36:57 pm
It doesn't need to be 'constant'. At worst, it needs to be frequent enough to keep the latency acceptably low. But if you are particularly concerned about latency then you could implement a long-running query on your public web server so that the Arduino can submit the HTTP request and then wait until either the server has an event to send it, or the server times out the request and sends a 'nothing yet' reply (so that the Arduino can then re-submit the query). This approach was popular during the early days of AJAX. It's less popular now but still viable and appropriate if you have a client that doesn't have support for the more general communication frameworks that are available now.
4623  Using Arduino / Project Guidance / Re: Aquarium Auto Top Off system on: September 20, 2013, 07:47:25 am
Is there any reason for the Arduino to be involved in the pump control, if it's ultimately going to be triggered by switches anyway?

Consider using a low voltage DC pump - it will be much safer in a DIY environment especially with water about.
4624  Using Arduino / Project Guidance / Re: Multi cylinder motorcycle ignition controller on: September 20, 2013, 07:44:05 am
The price I suggested was for a self-build system, which is the cheapest option. Every time I've done this in the past I seem to end up spending about £500 on the installation itself, in addition to the cost of the ECU. In that context, saving a hundred quid (or whatever) is not a big deal either way - and MS would save you an awful lot of design work. But, like you, I'm not interested in getting into an argument about money, it's your project to plan as you see fit, I'm just trying to make sure you have the information to make an informed decision.

With the Arduino approach the hard part with the hardware will be designing the I/O circuits to be robust and keep noise out of the Arduino. You can take inspiration from the MS circuit designs. The hard part with the software will get maintaining an accurate engine position signal especially at low speed when you are extrapolating over long periods while the engine speed is varying. Starting will be the hardest part to get right. Careful positioning of your crank position sensor (presumably a toothed wheel) would minimise that problem. Also pay attention to signal polarity and strength if you're using a toothed wheel since it will work (badly) the 'wrong' way round and the typical MVR sensor output amplitude varies with speed so you'll need to deal with big variations in amplitude through the rev range.
4625  Using Arduino / Project Guidance / Re: Arduino Mega + 1307 Time Clock gains almost a minute per day! Help! on: September 20, 2013, 07:31:19 am
Im using the <DS1307RTC.h> library which is linked to from the Arduino Library page so it should not be the issue?

I'm not familiar with the library and don't see it on the Arduino Library page, but it's possible that you are using it incorrectly. Does the library come with any examples? If so, I suggest you see whether any of those would enable you to check the accuracy of your clock.
4626  Using Arduino / Project Guidance / Re: Automation on: September 20, 2013, 07:25:31 am
I also want to allow my arduino to get a string that will then trigger an event on the arduino (light on/off).

Where does the string originate? Is it returning status data relating to the upload, or something initiated by another person, or what?
4627  Using Arduino / Programming Questions / Re: arduino and servo on: September 19, 2013, 07:59:49 pm
the stop and go back, but never do the real degree

Can you explain that a bit more clearly? The code should move the servo backwards and forwards between two fixed positions. Does it?
4628  Using Arduino / Programming Questions / Re: Is there any where to use a "make" utility with the IDE? on: September 19, 2013, 07:55:31 pm
"Everything" is not recompiled.  The interface is smart enough not to compile library code more than once.

I've read that more than once on this forum, but when I recompile a given sketch it seems to me the list of files that scroll past is just as long the second time as it is the first time and the compilation takes just as long.
4629  Using Arduino / Programming Questions / Re: [SOLVED] Truncated packets between Transmitter and Receiver. on: September 19, 2013, 07:51:06 pm
I don't see any obvious cause for the problem, but you're using vw_get_message() which I'm not familiar with. Where did you get your copy of the VirtualWire library from?
4630  Using Arduino / Programming Questions / Re: Out of RAM! How to get more? (optimize code help for a noob?) on: September 19, 2013, 07:39:12 pm
Im not following the button[0] part at the end?

This is the recommended technique for calculating the number of elements in the array: the size of the whole array in bytes, divided by the size of an individual element in bytes. You can hard-code the value instead, but that introduces the possibility of maintenance-induced errors since you have to remember to update the hard-coded value every time you alter the array size. One of the fundamental principles of good coding is that you should eliminate duplication - each thing should only be defined once. By calculating the array size rather than hard-coding it, you avoid having the array length defined in two places.
4631  Using Arduino / Programming Questions / Re: syntax for fscale code on: September 19, 2013, 07:32:35 pm
I haven't tested that function but it appears to have explicit support for negative ranges. Have you got a sample sketch we could run showing the incorrect values when you try to apply it to a negative range?

If you can't be bothered figuring out what the problem is, you could just negate the input motor_speed if it was negative, and then invert the result too.
4632  Using Arduino / Project Guidance / Re: letter substitution program on: September 19, 2013, 07:28:08 pm
Also look up the ascii encoding scheme, if you aren't already familiar with it. You'll need to understand this in order to know which element in your lookup table corresponds to which input character.
4633  Using Arduino / Project Guidance / Re: Multi cylinder motorcycle ignition controller on: September 19, 2013, 07:25:13 pm
I already posted that the Bowling and Grippo stuff has gotten too expensive (Megasquirt,

I didn't know what you considered 'too expensive' - you can get a self-build kit for a couple of hundred bucks which is pretty darned cheap in ECU terms. But if you want to design your own, you can use the MS I/O circuit designs for inspiration when you come to design your own I/O circuits. Either way the sensors, loom, connectors etc make a big contribution to the cost so I think it would be a mistake to think that the whole project is going to come in at half the cost (or whatever saving you're aiming for) with the Arduino option.
4634  Using Arduino / Project Guidance / Re: Getting stepper to step only when a signal is received on: September 19, 2013, 07:15:26 pm
Using a button to enter a number is easy enough, but would be very easy to get lost unless you provide some feedback to the user to show what value has been selected. If you only have a small number of possible values then you could just have one LED per option and turn on the LED for the selected value, moving to the next value each time the button was pressed and released. There are example sketches demonstrating how to debounce a switch input and detect changes in the input state.

If that was me I'd use an array of supported values and a variable which holds the index of the currently-selected value. Each time the button is pressed you increment the index modulo the number of values.

Then you can have a counter which is incremented each time the laser is detected, and if that increment takes it up to the selected value then reset the counter and move the stepper.
4635  Using Arduino / Project Guidance / Re: continuity tester on: September 19, 2013, 07:10:03 pm
There have been a couple of other threads about essentially the same problem in the last few weeks so I suggest you search those out to find what advice was given.
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