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16  Community / Bar Sport / Re: Is now the right time for a raspberry pi model B? on: May 31, 2013, 07:52:05 pm
Given the R-pi has been out for a year or so, I imagine so.  Frankly I haven't powered mine on for a long time, so  I can't say how stable they are.  You might want to read the R-pi forum to see what types of questions come up: http://www.raspberrypi.org/phpBB3/

Thanks. Registered. Now I'm known as liudr on raspberry pi forum smiley

Good. I'm Papa G there as well.
17  Community / Bar Sport / Re: Is now the right time for a raspberry pi model B? on: May 31, 2013, 06:49:23 pm
I am a kind of "hammering a refrigerator yourself" kind of guy. I don't mind doing all the ground work as long as it suits me smiley On the other hand, I can certainly use established web servers. I am going to have to learn or relearn perl, am I? I hate its syntax, sux.
All the gcc tools are available for the Pi. You don't have to use Perl. I use and like Python in addition to C/C++.
18  Using Arduino / General Electronics / Re: Close looped nature of circuits - WHY on: May 31, 2013, 06:17:28 pm
If the current flow into the load at Vout is small compared to the total current flow, then voltage at Vout is just the current times the resistance  of V2.

If that load is an analog input, very very little current flows, so the load is effectively 0 ohm, and Vout will equal Vin*Z2/(Z1+Z2) as described above.

Really?

19  Community / Bar Sport / Re: Is now the right time for a raspberry pi model B? on: May 31, 2013, 04:04:27 pm
Thanks guys. Out of impulsive shopping I pushed the button. Now it seems a decent choice. Thanks for the Debian link Papa G. I will need to learn linux somewhere so maybe I learn it with raspberry pi smiley

You're welcome! Surely you haven't escaped Unix in your university environment. It's quite similar. You'll pick it up quickly.

You'll find working with Apache, a real web server, far more satisfying than with Arduino.
20  Using Arduino / Networking, Protocols, and Devices / Re: Attiny45/85 with WIFI on: May 31, 2013, 11:11:56 am
45/85 + Raspberry Pi + wifi dongle is the most cost effective/least hassle method I have found. The Raspberry Pi + wifi dongle is going to run you around $55 with shipping in the USA.
21  Community / Bar Sport / Re: Is now the right time for a raspberry pi model B? on: May 31, 2013, 10:03:03 am
I've seen some comments on some websites regarding the stability of the model B with 512MB memory. I wonder if someone has some experience with it and whether you consider it safe to purchase. I don't want to end up paying for a platform in development but want to has at least some stability and reliability. Thanks.

I have three of the 512MB and one original 256MB model B's. They are all on my network via usb wifi modules like http://www.adafruit.com/products/814, and I log in headless via ssh. I am running the latest Debian distribution, Raspbian "Wheezy" from here http://downloads.raspberrypi.org/images/raspbian/2013-02-09-wheezy-raspbian/2013-02-09-wheezy-raspbian.zip

My reason for adopting the platform was to get past the frustration associated with using the Arduino platform to do anything network related that was more ambitious than the simple examples that ship with Arduino. The Raspberry Pi is fundamentally different from Arduino in that it runs a mature operating system, Linux, with all the software support that implies. I build simple shields with an Atmega 328 chip + peripherals to take care of the real time data acquisition and transfer the data serially to the Pi to take care of computation and display.

22  General Category / General Discussion / Re: X as the exponent on: May 18, 2013, 03:57:37 pm
And:

x = log2 18 / log2 5
x = 4.169925001442312 / 2.321928094887362
x = 1.79588894704536
etc., etc.
23  General Category / General Discussion / Re: Play-doh buttons and other things. on: May 17, 2013, 08:58:29 am
Love Jay Silver! Thanks for sharing.
24  Using Arduino / Project Guidance / Re: Feasibility of swim lap counter on: May 16, 2013, 12:26:01 pm
Someone mentioned that your feet touch the pool wall when you turn. If this is true, then could you hang a flat sensor board over the pool edge? A pressure activated switch could be used to increment a counter and a display (in a waterproof container) could be embedded in the board to display the laps underwater. A simple non-retriggerable one-shot multivibrator could be used to de-bounce the switch closure.

This is effective if someone had a personal lane. The touch pads are already in existence for races and events, though most are bulky.

Much of the time—in my case at least—lanes are split in half when I'm at a public pool. Which is why I was seeking a personal, portable solution that could clip onto a suit or goggle, or some sort of band that could be worn.
Okay, I see.

Water and air have similar magnetic permeabilities so perhaps a very strong magnet could be worn on your wrist or ankle and sensed by a coil of wire near the pool end wall. Suitable de-bouncing (seconds) would prevent multiple triggers during the turn.
25  Using Arduino / Project Guidance / Re: Feasibility of swim lap counter on: May 16, 2013, 12:10:25 pm
Someone mentioned that your feet touch the pool wall when you turn. If this is true, then could you hang a flat sensor board over the pool edge? A pressure activated switch could be used to increment a counter and a display (in a waterproof container) could be embedded in the board to display the laps underwater. A simple non-retriggerable one-shot multivibrator could be used to de-bounce the switch closure.
26  Community / Bar Sport / Re: My camera discontinued on: May 09, 2013, 12:29:26 pm
I sincerely hope that the prices don't rise any time soon. I still use my Hasselblad and enjoy getting great deals on used equipment. Many of the lenses have been out of production for years and their prices haven't appreciated as a result. I think it will be quite some time before it becomes a collectable.
27  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 11:52:19 am
Many Thanks Papa G

I really have learnt SO MUCH from this forum.   I am amazed at the number of regular replies by members whose level of knowledge I could only dream of reaching.

My project is moving forward and, strangely, I look forward to the next problem challenge smiley


You're welcome, DaveO. Somebody proposed that
Quote
“The beauty happens in the process. Not the final product.”
Have fun!
28  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 11:39:22 am
Can you post a link to the data sheet for this striker that you are using?

Unfortunately not. This is Africa.

All I can tell you is the specs we have, and 'Made in Spain'

Brand name is not relevant, as I can probably buy the exact same thing with 3 or more different names.



Okay, just curious. I wouldn't place to much weight on the data that you do have, in that case. Trust what you can measure and good luck with your project.
29  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 10:52:20 am
Quote
From my point of view, I have a striker rated 350mA for use on AC or DC, which I think should use around 350mA. The fact that my estimation of the size of power supply takes this into account, and I purchase the power supply, and it keeps failing because of the current being far in excess of the 'advertised' rating, becomes a problem for me - it's a matter of perception, you see.

Can you post a link to the data sheet for this striker that you are using?
30  Using Arduino / General Electronics / Re: Excessive current draw by strike lock on: May 03, 2013, 10:07:56 am
Quote
My last question would be :

The wall fitting AC adapter ( 230V to 16VAC 1A ) has 3 terminals. 2 would be the live / neutral. The third is connected directly to the earth pin that plugs into the wall.

Would it be recommended to connect spare wires in the cable to that earth terminal, and then at the gate location where the strike is, connect the same wires to the metal gate frame that the strike lock is inserted into ?

If it's a transformer, the 16VAC secondary should have no relationship, electrically, at all to anything on the primary including earth. The ground terminal is probably there to satisfy the need to blow the fuse/circuit breaker should a primary wire get loose inside the adapter.
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