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#1
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computer log when external switch is flipped?
How would I go about interfacing my computer to the outside world? I'm
wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? And of course I'll need some software. (I hope I don't have to write another device driver. It's been many years since I did that kind of programming. Someone else must have already written something. Someone else is probably already logging when their mailbox door is open/closed.) |
#2
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computer log when external switch is flipped?
David Deley wrote:
How would I go about interfacing my computer to the outside world? I'm wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? And of course I'll need some software. (I hope I don't have to write another device driver. It's been many years since I did that kind of programming. Someone else must have already written something. Someone else is probably already logging when their mailbox door is open/closed.) Back in the DOS days the parallel port was quite useful for the odd digital IO line. I presume someone makes USB digital IO cards nowadays - presumably someone must make one that to the PC appears like a serial port. -- http://www.petezilla.co.uk |
#3
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computer log when external switch is flipped?
David Deley wrote:
How would I go about interfacing my computer to the outside world? I'm wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? And of course I'll need some software. (I hope I don't have to write another device driver. It's been many years since I did that kind of programming. Someone else must have already written something. Someone else is probably already logging when their mailbox door is open/closed.) A parallel port is one interface. Another would be a hacked game controller (game port interface). Game controllers have switches on them, for firing, or selecting game options and so on. Both the old game port (15 pin) and newer USB game paddles might be candidates. The software interface would be a challenge. Companies in the business of making devices like that, probably bundle software to make it easier to use. Otherwise, you could need to do some programming of your own. (For example, with the game controller, you'd find the game controller API and program using it.) http://www.eagledaq.com/display_product_2620.htm Some other issues 1) Protecting your computer. Stringing a long wire and connecting it directly to a computer port, is asking for trouble. Even an adjacent lightning strike, could induce enough potential in the wire, to destroy the computer. Optical isolators are one way, of handling differences between subsystems, and affording some protection (if, say, AC from the wall came in contact with the secondary circuit). But this may not be enough to protect against lightning. The optoisolator needs its own power supply, but at least that power supply can be destroyed, without the computer being harmed. You would not extend power from a Molex on the computer, because that would be a path for lightning as well. http://en.wikipedia.org/wiki/Opto-isolator It can take a bit of imagination, to come up with sufficient isolation to satisfy this requirement. For example, if the post box had an AC switch, and switched an incandescent light on and off, which was mounted inside the house, you could use an optical detector tied to the computer, to detect the light. That would allow you to construct an enclosure for the light and detector, with some physical separation between the light, and the computer. That would achieve a much higher isolation voltage limit, than the 2KV to 5KV of a single optical isolator integrated circuit. 2) Scaring the Postman. Seeing wires, batteries, switches, in or around the postbox, is going to get you "no service" pretty rapidly. Your post office probably has a pretty extensive set of rules, for when to-your-door delivery will be denied. Even hinting that you're a "crazy person", is likely enough to get them to stay away. In terms of "not scaring the postman", you'd want a mechanism for the post box door, which provides no mechanical resistance. Again, that suggests an optical method. As long as there are wires stretching back from the post box circuit, there is still a need for isolation. So it will cost you one separate power supply, an optical interruptor detector type device, and the optoisolator at the computer end, to afford some protection. You can see some different kinds of optical devices here. http://dkc3.digikey.com/PDF/T091/P2466.pdf If the optical detection method could be done with fiber optics, that would allow a direct connection from the computer to the electronics (since a fiber optic cable by itself, would have no lightning safety issue). But that would likely be a nightmare to work out optically. (Dental plastic fiber might carry more light, than a telecommunications glass fiber, as the aperture and cross section might be wider. While the plastic fiber might be cheap to make, don't expect it to be cheap to buy.) If you need a source of inspiration, this Wikipedia article may help. I'd never heard of this person, until one day I was caught rigging up something out of bailing wire and binder twine, and someone mentioned the guy's name :-) http://en.wikipedia.org/wiki/Rube_Goldberg_machine HTH, Paul |
#4
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computer log when external switch is flipped?
Peter Chant wrote:
David Deley wrote: How would I go about interfacing my computer to the outside world? I'm wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? And of course I'll need some software. (I hope I don't have to write another device driver. It's been many years since I did that kind of programming. Someone else must have already written something. Someone else is probably already logging when their mailbox door is open/closed.) Back in the DOS days the parallel port was quite useful for the odd digital IO line. I presume someone makes USB digital IO cards nowadays - presumably someone must make one that to the PC appears like a serial port. See the discussion of older computers in the "Memory chip question" thread. Those things have everything you need. -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: http://cbfalconer.home.att.net Try the download section. |
#5
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computer log when external switch is flipped?
On Wed, 13 May 2009 01:51:57 -0700, David Deley
wrote: How would I go about interfacing my computer to the outside world? I'm wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? Better warn the post office ahead of time, you're likely to have the bomb squad there if you surprise any postman with a wired thingy in your mailbox. In fact they probably don't want to deal with it at all if it's a homebrew setup instead of a recognized, commercial product. |
#6
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computer log when external switch is flipped?
Good idea protecting the computer input. I hadn't thought that far yet.
I'm using "The MailMinder Wireless Mail Alert" device I purchased for only $12. A little transmitter box attaches to the mailbox door inside, detects when the door is tilted open and sends a signal. I was surprised the receiver actually worked in the house--I thought that would be too far away with too many walls blocking the signal. However, problems with the inexpensive receiver a .. There's no way to turn the receiver off .. There's no way to stop it from sounding an alert when you open the mailbox to insert outgoing mail, or to retrieve your mail. But for $12 it's a nice start. Thank you for all the suggestions. http://members.cox.net/deleyd/ Paul wrote: David Deley wrote: How would I go about interfacing my computer to the outside world? I'm wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? And of course I'll need some software. (I hope I don't have to write another device driver. It's been many years since I did that kind of programming. Someone else must have already written something. Someone else is probably already logging when their mailbox door is open/closed.) A parallel port is one interface. Another would be a hacked game controller (game port interface). Game controllers have switches on them, for firing, or selecting game options and so on. Both the old game port (15 pin) and newer USB game paddles might be candidates. The software interface would be a challenge. Companies in the business of making devices like that, probably bundle software to make it easier to use. Otherwise, you could need to do some programming of your own. (For example, with the game controller, you'd find the game controller API and program using it.) http://www.eagledaq.com/display_product_2620.htm Some other issues 1) Protecting your computer. Stringing a long wire and connecting it directly to a computer port, is asking for trouble. Even an adjacent lightning strike, could induce enough potential in the wire, to destroy the computer. Optical isolators are one way, of handling differences between subsystems, and affording some protection (if, say, AC from the wall came in contact with the secondary circuit). But this may not be enough to protect against lightning. The optoisolator needs its own power supply, but at least that power supply can be destroyed, without the computer being harmed. You would not extend power from a Molex on the computer, because that would be a path for lightning as well. http://en.wikipedia.org/wiki/Opto-isolator It can take a bit of imagination, to come up with sufficient isolation to satisfy this requirement. For example, if the post box had an AC switch, and switched an incandescent light on and off, which was mounted inside the house, you could use an optical detector tied to the computer, to detect the light. That would allow you to construct an enclosure for the light and detector, with some physical separation between the light, and the computer. That would achieve a much higher isolation voltage limit, than the 2KV to 5KV of a single optical isolator integrated circuit. 2) Scaring the Postman. Seeing wires, batteries, switches, in or around the postbox, is going to get you "no service" pretty rapidly. Your post office probably has a pretty extensive set of rules, for when to-your-door delivery will be denied. Even hinting that you're a "crazy person", is likely enough to get them to stay away. In terms of "not scaring the postman", you'd want a mechanism for the post box door, which provides no mechanical resistance. Again, that suggests an optical method. As long as there are wires stretching back from the post box circuit, there is still a need for isolation. So it will cost you one separate power supply, an optical interruptor detector type device, and the optoisolator at the computer end, to afford some protection. You can see some different kinds of optical devices here. http://dkc3.digikey.com/PDF/T091/P2466.pdf If the optical detection method could be done with fiber optics, that would allow a direct connection from the computer to the electronics (since a fiber optic cable by itself, would have no lightning safety issue). But that would likely be a nightmare to work out optically. (Dental plastic fiber might carry more light, than a telecommunications glass fiber, as the aperture and cross section might be wider. While the plastic fiber might be cheap to make, don't expect it to be cheap to buy.) If you need a source of inspiration, this Wikipedia article may help. I'd never heard of this person, until one day I was caught rigging up something out of bailing wire and binder twine, and someone mentioned the guy's name :-) http://en.wikipedia.org/wiki/Rube_Goldberg_machine HTH, Paul |
#7
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computer log when external switch is flipped?
David Deley wrote:
Good idea protecting the computer input. I hadn't thought that far yet. I'm using "The MailMinder Wireless Mail Alert" device I purchased for only $12. A little transmitter box attaches to the mailbox door inside, detects when the door is tilted open and sends a signal. I was surprised the receiver actually worked in the house--I thought that would be too far away with too many walls blocking the signal. However, problems with the inexpensive receiver a . There's no way to turn the receiver off . There's no way to stop it from sounding an alert when you open the mailbox to insert outgoing mail, or to retrieve your mail. But for $12 it's a nice start. Thank you for all the suggestions. http://members.cox.net/deleyd/ OK, I see there is some kind of receiver here, with a LED on it. Now, all you need, is a way to connect that to the computer. http://ecx.images-amazon.com/images/...4L._AA280_.jpg The easiest thing to do, would be to use your computer as a source of power for the receiver. The Molex disk drive connector has +5V and +12V on it. If you need some other voltage, you can use a three terminal regulator. For example, this one might make 3.3V from a 5V input for you. http://search.digikey.com/scripts/Dk...1086CSX-3.3-ND If the receiver used a 9V battery, you could use the 12V on the Molex, plus a three terminal (linear) regulator, to create 9V. http://search.digikey.com/scripts/Dk...LM2940T-9.0-ND There are various ways to get the signal from the LED on the receiver, into your computer. A photodarlington would be a relatively simple solution, but you'd need a light tight box around the photodarlington and the receiver LED, so only the LED could trigger it. This converts light, into an electrical signal. The Darlington pair is two transistors cascaded, so that the gain is higher. There might be sufficient gain, to drive a logic signal (like on a game paddle switch) directly. Darlingtons are not fast, but would be suited to the low speed detection, of a light or LED going on. The ones I have in my junk bin, don't have part numbers, and I fiddle with them until they work :-) http://search.digikey.com/scripts/Dk...&name=BPW38-ND You could also connect directly to the receiver circuit (open up the receiver, and add circuitry to it), but that is getting pretty complicated. If there is sufficient swing on the signal driving the LED, you might buffer a logic signal from that with a single transistor. Radio Shack still carries stuff like that. http://www.radioshack.com/product/in...ductId=2062586 But at least your $12 purchase, has solved most of the important problems for you. No lightning to worry about. Paul |
#8
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computer log when external switch is flipped?
"kony" wrote in message ... On Wed, 13 May 2009 01:51:57 -0700, David Deley wrote: How would I go about interfacing my computer to the outside world? I'm wondering if there's a way I can log the date/time when my USPS mailbox gets opened. Which eventually translates to I have a wire with a hi/low voltage for the mailbox is open/closed -- how do I connect that wire to the computer? What sort of input port is suitable for such a thing? Better warn the post office ahead of time, you're likely to have the bomb squad there if you surprise any postman with a wired thingy in your mailbox. In fact they probably don't want to deal with it at all if it's a homebrew setup instead of a recognized, commercial product. I don't know if it's still valid, but a mailbox, once installed, used to become USPS property. That's why those tubes had to be installed for newspaper delivery. |
#9
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computer log when external switch is flipped?
David Deley wrote:
Good idea protecting the computer input. I hadn't thought that far yet. I'm using "The MailMinder Wireless Mail Alert" device I purchased for only $12. A little transmitter box attaches to the mailbox door inside, detects when the door is tilted open and sends a signal. I was surprised the receiver actually worked in the house--I thought that would be too far away with too many walls blocking the signal. However, problems with the inexpensive receiver a . There's no way to turn the receiver off . There's no way to stop it from sounding an alert when you open the mailbox to insert outgoing mail, or to retrieve your mail. But for $12 it's a nice start. You must be able to acknowledge the alert. Simply do so when you return to the house. Please do not top-post. Your answer belongs after (or intermixed with) the quoted material to which you reply, after snipping all irrelevant material. Your failure has lost the entire previous quotations. See the following links: http://www.catb.org/~esr/faqs/smart-questions.html http://www.caliburn.nl/topposting.html http://www.netmeister.org/news/learn2quote.html http://cfaj.freeshell.org/google/ (taming google) http://members.fortunecity.com/nnqweb/ (newusers) -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: http://cbfalconer.home.att.net Try the download section. |
#10
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computer log when external switch is flipped?
CBFalconer wrote:
David Deley wrote: Good idea protecting the computer input. I hadn't thought that far yet. I'm using "The MailMinder Wireless Mail Alert" device I purchased for only $12. A little transmitter box attaches to the mailbox door inside, detects when the door is tilted open and sends a signal. I was surprised the receiver actually worked in the house--I thought that would be too far away with too many walls blocking the signal. However, problems with the inexpensive receiver a . There's no way to turn the receiver off . There's no way to stop it from sounding an alert when you open the mailbox to insert outgoing mail, or to retrieve your mail. But for $12 it's a nice start. You must be able to acknowledge the alert. Simply do so when you return to the house. Please do not top-post. Your answer belongs after (or intermixed with) the quoted material to which you reply, after snipping all irrelevant material. Your failure has lost the entire previous quotations. See the following links: http://www.catb.org/~esr/faqs/smart-questions.html http://www.caliburn.nl/topposting.html http://www.netmeister.org/news/learn2quote.html http://cfaj.freeshell.org/google/ (taming google) http://members.fortunecity.com/nnqweb/ (newusers) I hate bottom-posters. I have to scroll through everything I've already read before just to get to the new reply. (But for you I'll be nice and post this on the bottom.) |
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