How to improve reliability of header contacts?
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How to improve reliability of header contacts?

by petespaco on Sat Jan 04, 2014 10:33 pm

ATMega2560.
I have a fairly complex (for me) circuit that has about a dozen sensors, and LCD readout and a datalogger--- all built on one large solderless breadboard.
I have had trouble with the "zero" most of the eight pressure sensors shifting from time to time.
Suspecting bad breadboard contacts, I have wiggled the power wires from time to time and sometimes it helps, sometimes not.
If I shift from powering the device from the USB port to a 9volt supply, absolutely nothing changes. (A good thing).
As far as I know, there are three 5 volt pins on the 2560 that I can draw power from and I am using all three of them to power up the various power rails on the breadboard.
Today, it finally occurred to me that I haven't ever directly wiggled or remove/replaced the power lead from the 5 volt header pin of the "Power" header. Viola! problem solved.
I know I should solder the whole thing together and make it permanent, but this circuit is still mostly a prototype and still subject to major change.

Question:
What can I do to improve the reliability of these header contacts?

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Re: How to improve reliability of header contacts?

by franklin97355 on Sun Jan 05, 2014 12:37 am

Get better quality jumpers and correctly sized jumper wires (22ga if I remember) Insert the wires in straight and don't move them. Or get some of these http://www.adafruit.com/products/591 and solder (consider it an investment in mental peace)
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Re: How to improve reliability of header contacts?

by 1chicagodave on Sun Jan 05, 2014 3:00 am

I have a fairly complex (for me) circuit that has about a dozen sensors, and LCD readout and a datalogger--- all built on one large solderless breadboard.
I have had trouble with the "zero" most of the eight pressure sensors shifting from time to time.


Are you using the Arduino 5V pins to power the entire system?? :shock:
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Re: How to improve reliability of header contacts?

by petespaco on Sun Jan 05, 2014 11:56 am

To franklin97355:
I am using 22 ga solid tinned wire for jumpers for the power.
And yes, I do have a good supply of the "permanent proto boards". My sensor circuits are built up with them. I have also scratch built some small pc boards for outboard "traffic lights" that are all soldered. And I certainly do understand the "mental health" issue.
But since my current goal is to keep it flexible, I am looking for better connectors. I was thinking about cutting apart some female stacking headers to remove the individual pins. They are gold plated and have a pretty good "other end" for soldering my power wires to. They are also square in cross section, so one might have a better chance of multiple contacts in the "socket" than with round cross-section wire.
You make a good point, though. I think I did buy some spools of solid hook up wire that were NOT tinned. I, of course, DO tin the ends before using. I just looked up those 25 foot spools, ex: Adafruit ID 288, and I can't tell from the description if that material is tinned of not.

To 1chicagodave:
Yes, I am using the 5 volt pins to power the whole "down line" system (all the stuff outside the Arduino). I'd certainly like to take the power from someplace else, but I don't know where I'd get it. I'd be concerned that I'd screw up the regulation system somewhere along the line or that I would short something out on the Arduino board while soldering.

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Re: How to improve reliability of header contacts?

by adafruit_support_bill on Sun Jan 05, 2014 12:05 pm

I'd certainly like to take the power from someplace else, but I don't know where I'd get it.

If you have a 5v regulated supply, you can power everything (including the Arduino) with that. If you want to keep the Arduino power separate, just make sure you have a common ground connection between the Arduino and the rest of your circuitry.
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Re: How to improve reliability of header contacts?

by petespaco on Sun Jan 05, 2014 12:13 pm

Here's a youtube video of the device I have been talking about:

http://www.youtube.com/watch?v=RwoIPodGIQI

I know it's only of interest to "woodgas to electricity" people for the most part, so I won't be disappointed if you don't watch the whole thing.
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Re: How to improve reliability of header contacts?

by petespaco on Sun Jan 05, 2014 12:29 pm

Hello, Adafruit support.
That sounds like a great solution.
But I do see that I can't use a single separate 5 volt supply to run the whole thing since I can't plug 5 volts into the barrel jack (needs at least 7 volts, if I understand correctly).
So, am I correct in thinking that I need the following?:
ID 327 extension cable
ID 373 Jack
ID 1466 5 volt 4 amp PS

Then I will still need to power the Arduino itself from either the USB port (which I do when working on updates at the desktop pc) or the 9 volt wallwart when the system is out in the shop connected to the woodgas machinery. Is this correct?

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Re: How to improve reliability of header contacts?

by adafruit_support_bill on Sun Jan 05, 2014 1:03 pm

I can't use a single separate 5 volt supply to run the whole thing since I can't plug 5 volts into the barrel jack

You don't plug it into the barrel jack. You plug it into the 5v pin - bypassing the onboard regulator.
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Re: How to improve reliability of header contacts?

by petespaco on Sun Jan 05, 2014 1:28 pm

Thank you.
Parts are on order.

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Re: How to improve reliability of header contacts?

by 1chicagodave on Sun Jan 05, 2014 2:59 pm

petespaco wrote:Here's a youtube video of the device I have been talking about:

http://www.youtube.com/watch?v=RwoIPodGIQI

-----------------


Wow! That is an impressive amount of work put into that. I'm posting a screenshot from your video so others can appreciate the complexity of at least the breadboard part -

image.jpg
Full breadboard
image.jpg (73.85 KiB) Viewed 419 times

All the lights, hoses, and gauges connected outside of the box are pretty impressive too.

I can't really tell exactly what is digital vs. analog as far as what goes where. It does look like you have maybe 8 analog signals being read by the Arduino itself. Just from my experience with much smaller mixed projects, I'd strongly suspect you are getting a lot of signal noise on the power lines causing issues. And, on the video I saw the temperature reading jump up and down about 10° in a matter of seconds. If that's a rolling average with that large of swing....well.

You can think of the entire circuit as a complex system of thin, high-pressure water pipes with many outlet spigot/faucets throughout constantly being opened & closed at different frequencies. ...You already know how just a small leak can affect pressure.

Here is a few short articles which explain how power supply & circuit layout can affect analog signals & overall performance.

http://www.eetimes.com/document.asp?doc_id=1272289
http://www.analog.com/static/imported-f ... N-1103.pdf

I wouldn't even know where to begin turning your breadboard into a soldered PCB. But, I think your issue has less to do with contact/connection quality and a lot more to do with noisy/over-taxed power supply, signal 'crosstalk', and possibly even some other unwanted electrical phenomena from the breadboard and bundles of wires.

Are those graphs all from the data logger, or do you also have an oscilloscope? Exploring the different areas of your design with even a relatively inexpensive scope would possibly shock you and really help you understand what the individual signals really look like. Instead of a smooth line or the nice square digital signals you see in datasheets, it probably looks more like the "Eng" line on your data graph. :o

I'd suggest:

    • Trying to separate the the digital & analog power rails as much as possible and maybe using multiple regulated power supplies. (All grounds need to be connected, but things can be done to keep that somewhat isolated.)

    •Look into using decoupling/bypass capacitors for each major component or group/section. The important considerations are noisy digital vs. quieter analog circuits & making sure larger power consumers (like the LCD) don't steal power from nearby components.

    •Using the AREF pin (and add code to use it). The idea is to have the voltage at AREF match as closely as possible the exact voltage being used by the analog sensor device. That way any voltage fluctuations at the sensor are reflected at AREF, and the Arduino will use that as reference for measurement, keeping the readings much more accurate.

There are a lot of articles & resources about mixed signal circuit and power supply designs. Just google around. Analog.com is also full of great searchable technical reference.

Good luck! I may be watching for updates on your website...

Just for my own interest - When did you start building/using that Arduino sensor project?
Please forgive my hyperanthropomorphization.
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Re: How to improve reliability of header contacts?

by michaelmeissner on Sun Jan 05, 2014 6:15 pm

If you haven't seen it already, you might look at my reply today to a different person: http://forums.adafruit.com/viewtopic.php?f=47&t=47926
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Re: How to improve reliability of header contacts?

by petespaco on Mon Jan 06, 2014 9:08 pm

Thank you guys for your most recent posts.
If you think the breadboard looks bust and/or messy, you ought to see the code!
I have stuck the scope on a couple of the output lines of sensors and the noise isn't getting them as far as I can see. And, I THINK I have looked at the 5 volt line for noise too. But you raise good questions so, if it ever warms up around here, I'll do more investigation along those lines.
Another thing I have thought about but not done yet is to simply measure the current being drawn from by the sensors and by the system as a whole. I just spent about an hour trying to locate and add up all the currents required by the various components and finally gave up. You wouldn't think that would be all the hard, would you? I did find that the pressure sensors apparently only need about 7ma each. But I am suspicious of the LCD display (as a possible current hog) if anything.
One of you mentioned a 10° change in temp on a graph at one time. The temps are NOT averaged. A change that small doesn't bother me. I can see that really happening.
So I am going to beef up the power supply anyway.
Regarding the Canadian connector pin supplier: Can an American buy from them? I tried to buy some stuff from "Princess Auto", a (I think) and they said they couldn't ship to the USA.
I have spent a lot of time trying to relate some of those spikes to something I can get my arms around but there's a lot of liquid and air column oscillation to contend with, too.
----Keeps me out of the bar pretty well.

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Re: How to improve reliability of header contacts?

by michaelmeissner on Mon Jan 06, 2014 9:38 pm

Regarding the Canadian connector pin supplier: Can an American buy from them? I tried to buy some stuff from "Princess Auto", a (I think) and they said they couldn't ship to the USA.


I live in Massachusetts, and I've ordered from dipmicro quite a few times. They will either mail from Niagara Falls, Ontario where they are located or they have a courier that crosses over the border and mails from Niagara Falls, NY. Generally ship times are very fast (competitive with adafruit).

This quote is on their site about whether you would have to pay brokerage fees.

USA: No, but your order may be split into multiple separate shipments delivered at no additional cost as Americans are allowed up to $200 exemption per entry. Our courier currently has 2-3 entries to USA weekly, so if you order for $800, it may take up to 2wks between first and last delivery. We can always accomodate customers who can expense taxes and duties and want their items fast, we can deliver to entire continental USA in 1 day for $35 for first pound.


Given their prices, it would take quite a few components to get over the $200 limit. They quote $3.50 (Canadian, though right now USA/Canadian are fairly close) for small packages shipped standard, and $7 for priority and larger packages.
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Re: How to improve reliability of header contacts?

by petespaco on Tue Jan 07, 2014 4:02 pm

Re: Plugging my new, soon-to-arrive 5 volt regulated supply in to the 5 volt pin on the Arduino:
I assume, Adafruit support, that you mean that I should plug the output of my new 5 volt supply into any one of the three 5 volt headers on the Arduino. If I do that, and then run parallel leads from that power supply to all of my other stuff, it should work. Is that correct?

But, having done that, can I still plug the Arduino into the USB port of the computer to load new code, look at the serial interface, etc.? Will there be a problem with the regulator on board the Arduino fighting with the external power supply?

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Re: How to improve reliability of header contacts?

by adafruit_support_mike on Wed Jan 08, 2014 1:59 am

petespaco wrote:I assume, Adafruit support, that you mean that I should plug the output of my new 5 volt supply into any one of the three 5 volt headers on the Arduino.

Yes. The one in the 'power header' is generally preferred.

petespaco wrote:If I do that, and then run parallel leads from that power supply to all of my other stuff, it should work. Is that correct?

Correct.

petespaco wrote:But, having done that, can I still plug the Arduino into the USB port of the computer to load new code, look at the serial interface, etc.?

Hmm.. I had to dig through the schematics to find an answer to that one: don't do that while supplying power to the 5v pin.

petespaco wrote:Will there be a problem with the regulator on board the Arduino fighting with the external power supply?

Yes. The 5v pin connects directly to the Arduino's regulated voltage supply rail, so connecting to that pin bypasses the circuit that decides what power source to use. That isn't bad per se, it just means you become responsible for managing the power connections.
When you void a product warranty, you give up your right to sue the manufacturer if something goes wrong and accept full responsibility for whatever happens next. And then you truly own the product.
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