Idea for motorhome gadget? (1 Viewer)

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Gromett
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@Gromett
Are you a professional with all these whizz bangs, or are you a self taught hobbyist.
Whichever, I'm well impressed.(y)

I got a BTEC onc in electronics back in the late 80's, Got my RAE C&G when I was 14. But I left the electronics field in 1990 when I got a job writing games :) I have been in computers ever since. My memory of the details of electronics is therefore extremely rusty but digital electronics is much simpler than analogue. And with my Assembly language experience I understand microprocessors at a low level (although rusty on that as well). That is part of the reason I want to do this to refresh my memory. I also used to love electronics until it became a job. I repaired TV/VCRs for a while and that was enough to put me off it for a long time.
 

JimJams

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weather forecsting stone.png


Easier lol
 
OP
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Gromett
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Just having a flip through the various arduino sites and found this...

https://www.sparkfun.com/products/10245

Broken Link Removed

I am thinking of using this as a way to measure the contents of my gas cyclinders. I will weigh them when empty, fill em up and weigh them again using this sensor. Using the above mentioned chip I can transmit the data and perform not only current level measurements. I could graph over time, give estimates of time till empty etc...

Not sure how accurate the sensor would be due to the cylinder shifting during driving. However at £6.61 each it is worth a punt.

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Sep 24, 2013
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Grommet, I'm coming up to retirement from 40 years in the electronics design sector. Started working with TTL but moved over to microprocessors when they became mainstream. I've been playing with the Pi on one off but it's a bit of an overkill for small hobby stuff but it was cheap and all on one pc. I still hand wire prototypes but with the size of components and my eyesight it's not so easy nowadays. Your Arduino project has pointed the way to a much better path I think. I hadn't realised just how prolific these things are or how cheap they are when ordered from overseas. Is the development software as easy to use. I would like to write in C. And the big plus is that you can do all this when away in the motorhome with just a laptop.
By the way, one of my recent projects involved load cells. Four wire Wheatstone bridge devices, not as simple as the one you highlighted.

Edit: Just been thinking on your load cell idea. Gas bottles are normally strapped in. To weight it they need to be free standing unless they are in a close fitting sleeve which is strapped down (can go up and down but not side to side).
 
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OP
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Gromett
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Grommet, I'm coming up to retirement from 40 years in the electronics design sector. Started working with TTL but moved over to microprocessors when they became mainstream. I've been playing with the Pi on one off but it's a bit of an overkill for small hobby stuff but it was cheap and all on one pc. I still hand wire prototypes but with the size of components and my eyesight it's not so easy nowadays. Your Arduino project has pointed the way to a much better path I think. I hadn't realised just how prolific these things are or how cheap they are when ordered from overseas. Is the development software as easy to use. I would like to write in C. And the big plus is that you can do all this when away in the motorhome with just a laptop.
By the way, one of my recent projects involved load cells. Four wire Wheatstone bridge devices, not as simple as the one you highlighted.

I believe the dev environment is easy to use. Not played with it myself yet but watched lots of videos. The language is based on C I believe if not C itself. I will probably be dropping down to ASM when not using the libraries. Not totally sure how it will play out yet.

The load cells I linked to will probably need a wheatstone bridge configuration as well. The swing is not big enough even with an amplifier on a single device. Especially as I will be measuring under 50% of it's spec.

I will be using vero board (or whatever it is called these days) to do the ones for my van. If I come up with anything useful, I will probably look at getting the PCB's made by a PCB shop. Can't be bothered to make my own these days. Plus environmental laws have changed since I last made my own. Disposing of the used acid will probably be a nightmare now?

The spec sheet for the ATTiny85 is very interesting. I can't believe how feature rich this $0.99 8 bit microprocessor actually is. Incredible.
http://www.atmel.com/devices/attiny85.aspx

Please let me know if you do any work with the arduino. Will be very interested :)
 
OP
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Gromett
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By the way, one of my recent projects involved load cells. Four wire Wheatstone bridge devices, not as simple as the one you highlighted.

Edit: Just been thinking on your load cell idea. Gas bottles are normally strapped in. To weight it they need to be free standing unless they are in a close fitting sleeve which is strapped down (can go up and down but not side to side).

I have discovered that the load cell I linked won't do the job. A lot of project sites recommend stripping scales for parts as it works out cheaper. I am considering something like this.

www.ebay.co.uk/itm/361438128178
I am going to buy one and strip it down....

As for the weight. I don't think the straps will affect the weight measurement beyond the margin of error of the scales.

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Minxy

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Gromett, I understand some of the above 'computer' chatter but one thing has occurred to me regarding the bottle weighing device using the postal scales you've mentioned ... if they're anything like the digital scales I used at home they have an automatic reset to zero when they're first turned on so if your bottle was sat on the 'adapted' device you might find that it won't read above zero unless you turn it on without the weight of the bottle on first. Whether the postal scales have a way to get round this I don't know but I can't see anything in the blurb although it does mention the tare/net weight but that's not the same.
 
OP
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Gromett
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Gromett, I understand some of the above 'computer' chatter but one thing has occurred to me regarding the bottle weighing device using the postal scales you've mentioned ... if they're anything like the digital scales I used at home they have an automatic reset to zero when they're first turned on so if your bottle was sat on the 'adapted' device you might find that it won't read above zero unless you turn it on without the weight of the bottle on first. Whether the postal scales have a way to get round this I don't know but I can't see anything in the blurb although it does mention the tare/net weight but that's not the same.

I won't be using the scales themselves. I will be disconnecting the sensors from it and creating my own "brain". I am looking at these scales as they are pretty accurate and dirt cheap hence I can afford to knacker them up during the butchering stage :)
 

Minxy

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I won't be using the scales themselves. I will be disconnecting the sensors from it and creating my own "brain". I am looking at these scales as they are pretty accurate and dirt cheap hence I can afford to knacker them up during the butchering stage :)
If you can do 'brain surgery' then you'll probably be able to bypass the auto zeroing bit ... oooo .... just though of a film for you ... "The Man with Two Brains" ... assuming of course that you've got a 'full' one yourself! :D

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Sep 24, 2013
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Grommet, we have just used very similar scales (four loadcells...one in each foot) to upgrade one of our products (we make talking equipment for visually impaired people). So you will have four load cells to interface into. I believe the manufacturer combines these together. Somewhere in there you will find an analogue representation of the load. The circuitry will not be sophisticated. It is surprising what the Chinese can do with a single op amp! However you could just find a black blob! But the analogue stuff is probably discrete.

On the processor front you will find that a lot of Microchip PICs (also RISC devices) are similarly priced. I use an 8 pin one which are about 40p to us.
 
OP
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Gromett
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Grommet, we have just used very similar scales (four loadcells...one in each foot) to upgrade one of our products (we make talking equipment for visually impaired people). So you will have four load cells to interface into. I believe the manufacturer combines these together. Somewhere in there you will find an analogue representation of the load. The circuitry will not be sophisticated. It is surprising what the Chinese can do with a single op amp! However you could just find a black blob! But the analogue stuff is probably discrete.

On the processor front you will find that a lot of Microchip PICs (also RISC devices) are similarly priced. I use an 8 pin one which are about 40p to us.

This is one of the many sites I found that recommend cannibalising.

http://www.open-electronics.org/wi-fi-body-scale-with-arduino/

I will be taking it a step further by removing the sensors from the glass plate and totally discarding the electronics. I will use my own amp circuit to feed a (max) 5v to the analogue input pin on the Micro controller. I want direct readings. I will take a reading when the tank is empty and another when it is full. This will set the range. I don't believe the sensors are linear but they should be close enough for my purposes. I will transmit the data over a radio link on the 2.4Ghz unlicensed band to my main Arduino in the van.

I will replace the glass plate with a 3-4mm aluminium plate to avoid corrosion and to protect the sensors from being dinged. This will only be designed to be used with refillable gaslow/gasit cyclinders. I suppose it could be used on swappable cylinders but I would have to make it more rugged.

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OP
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Gromett
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PS: Arduinos run a subset of C++ But you can dump the Arduino boot loader and use the GCC C compiler directly but you would lose a lot of the community support stuff.
 
Sep 24, 2013
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I think community support if quite crucial for beginners to the subject. So will stick with a C++ subset. I still think you will come a bit unstuck with your idea for gas levels. The holding straps are going to introduce a lot of error I feel unless you are going to have a less than tight securing system. You may find otherwise in practice of course. Is there a way to check that out with ordinary scales before you launch into a lot of work?
 
OP
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Gromett
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I think community support if quite crucial for beginners to the subject. So will stick with a C++ subset. I still think you will come a bit unstuck with your idea for gas levels. The holding straps are going to introduce a lot of error I feel unless you are going to have a less than tight securing system. You may find otherwise in practice of course. Is there a way to check that out with ordinary scales before you launch into a lot of work?

In my van there is no holding straps. I am in a self build. The gas cylinders are in a tightish fitting box. They aren't going anywhere.

I honestly don't believe the straps have any effect on the downward force applied by the cylinder to the base. The straps are simply to stop them moving about. In my previous vans I could never get them tight enough to immobilise them totally.

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Sep 24, 2013
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Ahhh I see. That would make a difference. In that case my comments are not relevant. I'll watch you progress with interest.
 
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Gromett
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Ahhh I see. That would make a difference. In that case my comments are not relevant. I'll watch you progress with interest.
Thanks Steve, Please keep me posted on anything you do with the Arduino. I am extremely grateful for your comments and any advice you can offer in future :)
 
Sep 24, 2013
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You mentioned about getting pcbs made. There are a few pcb houses that do prototype quantities. PCB-pool is one of them that I use. Components are so small nowadays that breadboarding is something I try to stay away from. I go straight for pcb first then software after. If you can arrive at a common circuit board that serves several sensors (and it sounds as if you are planning on several) than you can do a pcb that has stepped and repeated circuits. PCB-pool for instance charge for a minimum of about 4 inches square. If you have say a dozen small boards repeated then it works out for a few pounds per circuit. Look them up. There are ways to keep the cost down.

If you need any help with pcb design then I'd be happy to help. Just send me a hand drawn schematic. In the company I work for you have to be a jack of all trades so I design the hardware and the software as well as the housings that they fit into.

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OP
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Gromett
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You mentioned about getting pcbs made. There are a few pcb houses that do prototype quantities. PCB-pool is one of them that I use. Components are so small nowadays that breadboarding is something I try to stay away from. I go straight for pcb first then software after. If you can arrive at a common circuit board that serves several sensors (and it sounds as if you are planning on several) than you can do a pcb that has stepped and repeated circuits. PCB-pool for instance charge for a minimum of about 4 inches square. If you have say a dozen small boards repeated then it works out for a few pounds per circuit. Look them up. There are ways to keep the cost down.

If you need any help with pcb design then I'd be happy to help. Just send me a hand drawn schematic. In the company I work for you have to be a jack of all trades so I design the hardware and the software as well as the housings that they fit into.

Thank you :)

I can design my own PCB's or at least I used to be able to lol. I wrote some software back in the 80's that controlled a plotter to draw my designs onto acetate sheet which I then used in a UV box... Ahhh, Memories :)

I will be designing on a bread board first and writing the software. I am newly back to this so I am sure I will forget things like smoothing caps and pull up resistors sometime.... Going straight to PCB is not really practical for me. I will use vero board for my own projects, and only go to PCB's if others want them made which I can't see being likely but you never know.

You are correct on the sensor board though. The voltage sensor boards would need a potential divider, weight sensors would need an amp circuit etc etc. Rather than doing separate boards for each I would do a single board that is capable of handling all types of my inputs. Shouldn't add to the size but would make it flexible and cheaper to produce. The only downside is I won't be able to design and build the nRF24L01P chip onto the circuit so that will always be a separate board. I don't like the idea of using the piggy back method the arduino shields use.. My other thought is to use pcb risers and a very short length of ribbon cable directly soldered. If you have any suggestions on this one I would appreciate it... This is the transceiver board I will be using. Broken Link Removed I don't want to solder it directly to my board.
 
OP
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Gromett
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I have decided on the order that I am going to be doing these projects now.
I will be doing the 12v battery voltage monitor/alarm first. Then the gas cylinder gauge and finally the accurate water tank sensor.
I will probably knock up the light switch controller pretty quickly but that is a simple relay driver so I guess it will only take me an hour or two.
 
Sep 24, 2013
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Hi Grommet,
Arduino delivered (from a supplier 15 miles from me!). Just a one off. Also have a microphone amplifier. I want to detect dog barks and then generate an ultrasonic signal too "discourage" them.
I have tried the standard Arduino hobbyist programming environment but have also downloaded the Atmel Studio 7 IDE (very big download!). I'm more used to that sort of development environment but I can see the advantage of the hobbyist one. So much simpler and less intimidating. I'll probably stick to that one for the time being.

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Hi Grommet,
Arduino delivered (from a supplier 15 miles from me!). Just a one off. Also have a microphone amplifier. I want to detect dog barks and then generate an ultrasonic signal too "discourage" them.
I have tried the standard Arduino hobbyist programming environment but have also downloaded the Atmel Studio 7 IDE (very big download!). I'm more used to that sort of development environment but I can see the advantage of the hobbyist one. So much simpler and less intimidating. I'll probably stick to that one for the time being.
Good luck with it :) How are you going to distinguish between a dog bark and any other noises?
 
Sep 24, 2013
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At the moment most of the loud noises in my neighbourhood are dogs barking. I'll have to do some analysis of the waveform envelope perhaps. Barks have a fairly short attack time. I don't think the Arduino has the MIPS (or program space) to perform a Fourier analysis, even if I knew how to do the programming!
 
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Gromett
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At the moment most of the loud noises in my neighbourhood are dogs barking. I'll have to do some analysis of the waveform envelope perhaps. Barks have a fairly short attack time. I don't think the Arduino has the MIPS (or program space) to perform a Fourier analysis, even if I knew how to do the programming!

Perhaps measure the frequency and put a band pass filter on the input then trigger on the level?

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Sep 24, 2013
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Different dogs as my neighbour takes dogs in for her friends so frequency scope is quite wide. But certainly worth a look at. I need to do some recordings and examine the waveform.
 
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Gromett
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My order from Bangood arrived earlier this year but there were some parts missing. Then I got time poor due to work again. However the order for the rest of the parts is now in :)

Should arrive before the end of the month (y)

I have the parts for 2 projects organised in full now.

The first is a remote battery monitor for my van battery.
The second is a temperature controlled fan with a twist.

I will be posting pretty soon after the parts arrive with progress :D
 

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