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31  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 09:41:00 am
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I think that this problem should not be 'solved' ( masked ) with this solution.  With the very low resistance on the coil, I think that it would continue to drain current in an ever increasing manner, until either the power supply peak is exceeded ( like happening now ) or the 2 second that is coded for the coil to be energized has elapsed.  Only difference with the old supply, was that it was capable of managing the short for the 2 seconds and didn't quite reach its peak.

If I am understanding this problem correctly, I think that the stress placed on the components in the old power supply by this action was a major contributor to its' demise.

First off, you are assuming a "problem" where none necessarily exists. The current that your coil consumes on DC is a matter of Ohms Law for the most part. If you want to lower the current on DC then your option is to replace the strike with one that consumes less current. If the failure of the original power supply was from being overstressed, then it was misapplied in the first place and should be replaced with one with even greater ampacity, not less as you evidently did.
32  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 08:54:56 am
You likely chose to use DC for your strikes so that the system could be operated by battery backup. If you switch to AC for one or both of the strikes, obviously, that will no longer be an option. As the problem with DC is that your power supply is not capable of supplying the current to operate the strike, if you want to maintain the battery backup capability, one solution is to use a power supply that can supply enough current. As suggested in reply #16.
33  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 08:27:51 am
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To solve the problem of not having a gate lock : if I want to connect the striker to one of these AC adapters, would it be safe to connect 1 of the AC lines directly and permanently to the striker ( like I currently have the 12VDC Ground connected ) and pass the other line through my relay ( com to no pins, controlled by the Arduino ) ?
Yes, obviously making sure to isolate both the AC leads from Ground.

Does it matter which line I use for the permanent connected line ?
No.

Should the striker still have a diode over the contacts, or is that not applicable if I am using an AC supply ?
No diode.

Is it possible that a coil that draws 3.3 A on a 12VDC circuit, would draw less than 1A on 16VAC ?
Yes, very likely.
34  Community / Bar Sport / Re: Carbon Monoxide + IBM = Animated Movie? on: May 02, 2013, 01:38:40 pm
That's very impressive.
35  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 02, 2013, 12:07:07 pm
It is a 12V system, and the resistance over the coil is 24 ohms ( yes, measured with a multimeter ). This means the current should be 500mA.  So how could it possibly consume more than 6 times that ?

So, you have measured the actual current consumption with a multimeter? As in multimeter in series with load. Have you substituted a hefty 12V battery for the 12V power supply? Do you get the same current printouts with the battery substituted for the power supply?

I wouldn't worry about damaging the battery for a short test.


No, not the consumption. I measured the disconnected coil over the 2 terminals and got a reading of 24 ohms.

You are suggesting powering the coil with something like a car battery ( the strike is rated, I think, from 8 to 18V ) with an amp meter in series and seeing the reading ?

I am off to the local auto electrician first thing in the morning to get the car aircon repaired, and will take the lock with me. I am sure he would have a decent amp meter ( which I do not - yet - have ).

Yes, that is what I'm suggesting. Get a cheap Chinese multimeter as well. I paid $10 for the one I use when I'm working on my vehicle.

How about a schematic of what you have wired up?  I am not convinced from your various descriptions that things are wired correctly.

Sounds like a reasonable idea - give me an hour ( hopefully ) to get the kids into bed and I will sketch it out.


Excellent suggestion.
36  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 02, 2013, 11:54:50 am
It is a 12V system, and the resistance over the coil is 24 ohms ( yes, measured with a multimeter ). This means the current should be 500mA.  So how could it possibly consume more than 6 times that ?

So, you have measured the actual current consumption with a multimeter? As in multimeter in series with load. Have you substituted a hefty 12V battery for the 12V power supply? Do you get the same current printouts with the battery substituted for the power supply?

I wouldn't worry about damaging the battery for a short test.
37  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 02, 2013, 11:45:06 am
Again, have you tried powering the system directly from a 12V battery? How much current does the strike in question draw when measured with a multimeter?
38  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 02, 2013, 10:50:19 am
Thanks Papa G

I have little doubt that a power supply with a higher peak rating ( like the previous supply ) would most likely survive the excessive current draw for the short period that the strike is energized.

But it still doesn't explain why a 350mA strike is drawing 3A which causes the existing supply to reset.

It is also quite possible that the 'expiry' of the old power supply could have been caused by this excessive draw, having placed strain on the components.

I was prepared to isolate the power to the strike by adding a separate power supply / transformer just for the strike locks, but I think that I first need to try to understand why it is happening.

So I am back to the question of why the fuse didn't blow, and is the 3A diode in line after the fuse protecting the fuse, but failing because of the current ?



You're measuring the current via the hall effect device, right? Can I presume that you are reading it via an analog in on the Arduino? If so, then imagine this:

the current demand on the new supply causes its voltage to drop below the dropout voltage of the Arduino regulator and the supply voltage to the microprocessor drops to say, 3.5V. If at that time your sketch reads the analog input for the hall effect (current sensor) it will use the 3.5V supply as the reference for the ADC but your calculation will be done assuming a 5V reference and the result will be a higher than actual current. Just a theory, mind you. smiley
39  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 02, 2013, 10:05:25 am
Did everything work before you replaced the power supply?

Excellent question. The previous supply died the day before, and I only noticed 6 hours later when the battery shut down.

The exact cause - not sure. I have not had the time to spend on the old supply PCB, but since it has some components that I do not recognise, and a couple of really large capacitor looking thingy-ma-goodies ( read : 'i don't' really understand what I am looking at' ) , I will most likely err on the side of caution and just discard it.

Also, living at the coast, we do get a large amount of corrosion and have grown to accept that things do deteriorate faster here.

Did it all work before ?  Yes.  But I think that the previous supply may have had a higher peak rating, so it may have just managed to supply the short drain for the 2 seconds that the relay was on, before shutting itself down.

I may have missed it in another comment but have you tried running the system directly from a 12V battery, thereby eliminating the power supply? It's entirely possible that what I highlighted in red has been the answer all along and you just need to fit a heftier power supply.
40  Community / Bar Sport / Re: My camera discontinued on: May 01, 2013, 09:37:29 pm
Yes, I'm a little surprised they stayed in production as long as they did. Fortunately, there seems to be plenty of used stock around which will probably outlast me.  smiley
Well the supply of film for the camera and chemicals to develop it may be more of an issue than just the body and lenses.  While medium format and large format still have toeholds and it has become a niche market, I would imagine the consumer 35mm film infrastructure to completely disappear within the next few years.

There is a lab in Dallas that still processes different kinds of film and does drum scans of the negatives. There is not as good a selection of films now.

Yes, with the DSLRs available today, there is really no advantage to shoot 35mm anymore.
41  Community / Bar Sport / Re: New Logo Design for Solar Energy International on: May 01, 2013, 09:20:06 am
I can't really comment on how good a logo it is, but as art, I like it.

The metaphor of Earth as energy source in place of the Sun, with people as rays of light, radiating their existence into the void of space as we squander our precious resources, is very powerful.
42  Community / Bar Sport / Re: My camera discontinued on: May 01, 2013, 09:09:18 am
To the OP, while it was perhaps inevitable, I can feel your pain.  I've never handled a Hasselblad, but they certainly were classic, iconic cameras.

Yes, I'm a little surprised they stayed in production as long as they did. Fortunately, there seems to be plenty of used stock around which will probably outlast me.  smiley
43  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: April 30, 2013, 05:59:25 pm
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I have just replaced a power supply.

Why?

Did everything work before you replaced the power supply?
44  Community / Bar Sport / Re: My camera discontinued on: April 30, 2013, 05:29:40 pm
I still use a Pentax MX SLR given to me in 1979.
It's a lot lighter and more compact than my new K5, but the K5 can still use the same glass I've been collecting for the last thirty-odd years.
Good thinking, Pentax.

It's good to be able to use old glass because in most cases it's better than the new stuff. That's certainly the case with the Zeiss lenses for my Hasselblad. I like the fact that a vintage $5000 lens is worth $0.10 on the dollar nowadays too. I just acquired a 250mm lens (about 3X optical) for $300 that would have cost as much as a good used car when new.
45  Community / Bar Sport / Re: My camera discontinued on: April 30, 2013, 03:53:35 pm
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Twelve Hasselblads remain on the lunar surface.

I wonder if they are still under warranty?

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My Hasselblad 500C/M that I've had since the early 70s is now discontinued tech. Not a bad run.

Can you still get film for it?

Can still get 120 roll film but not as good a variety as in the past. If you want to wind your own 70mm cassettes there are some movie films that are interesting.
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