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16  Using Arduino / Project Guidance / Re: CO Alarm on: November 17, 2012, 10:47:08 pm
Thanks Hazard, here are pictures of the relay... the horn is nothing special, just a pos/neg post on it. The specs are 18amps/12v.
17  Using Arduino / Project Guidance / Re: CO Alarm on: November 17, 2012, 09:32:31 pm
LOL good one... yeah it is VERY loud ... you'd think there was a semi in the house .... my electrical background is very poor it's been ages since school and I'm not even sure I know what a "common ground" is... the relay has 5 pins 30, 85,86, 87 and 87a (in the middle). Every article I read on relays tells me something different and then people post saying that the article is wrong, I have yet to find two articles that agree on which pin is what. From what I gather the 30 in the signal input for the Arudion and 85 and 86 are the coils pos/neg I'm using an old ATX power supply (the yellow and black wires, 12volts) to sound the horn. Don't know where to hook both grounds, one coming from the power supply should go to the horn, would I connect the 5v Arduino ground to the horn also? Forgive me for being so confused, just not sure how everything goes.
18  Using Arduino / Project Guidance / Re: CO Alarm on: November 17, 2012, 08:37:57 pm
OK I think I'm going to hold off on this for a bit until I have a better understanding of what I need to do. This relay I have is rated for 30 amps and the horn specs says it draws up to 18 amps. I think the optoisolator sounds like the best idea so far to avoid frying the Arduino. I just don't know where I can find one that would handle 18 amps. All the ones I'm seeing are rated much much lower than that.
19  Using Arduino / Project Guidance / Re: CO Alarm on: November 16, 2012, 12:19:02 pm
Thanks Hazard, I have a diode on the output .... I'll stick a resistor on the neg side... the neg of the external power supply, not the Arduino correct?
20  Using Arduino / Project Guidance / Re: CO Alarm on: November 16, 2012, 11:23:07 am
Ok guys I promise I will stop with the dumb questions... I have a 5 prong relay, I understand where the wires go except for the "trigger" from pin 12 on my Arduino ... using digitalWrite HIGH signal to activate the relay... where do I ground pin 12? To the 12v power supply? It seems if I ground to the Arduino it isn't a complete circuit. Please go easy on me I'm on my first cup of coffee. :-)
 
21  Using Arduino / Project Guidance / Re: CO Alarm on: November 16, 2012, 05:27:30 am
Well between 1978 and now I've had 5 babies and have managed to not fry or gas any of them so I'm 0 in 5 in that category haha. I think it's great that you guys share your knowledge and we all enjoy "playing" with our Arduinos. Since I am new to this where do you guys prefer to order your parts? I'd like somewhere in the U.S.A. that is priced reasonably with fast shipping and good customer service. Of course I'd pay slightly more providing the last two criteria were exceptional.
22  Using Arduino / Project Guidance / Re: CO Alarm on: November 15, 2012, 06:39:41 pm
No, not for any "real" protection ... I have a propane heater I use in the garage once in a while and I am the only one out there tinkering. I never let it burn more than 10 mins and always leave the door up a few inches just to be sure. Just more of a "tinker" thing.
23  Using Arduino / Project Guidance / Re: CO Alarm on: November 15, 2012, 05:02:35 pm
Thanks guys for the help ... I know the really simple solution would be just buy a CO Detector on Amazon but that would take all the "fun" out of it lol .... thanks again.
24  Using Arduino / Project Guidance / Re: CO Alarm on: November 15, 2012, 04:05:23 pm
I believe I have some Schottky diodes around here ... would they be sufficient?
I also have some http://www.datasheetcatalog.org/datasheet/diodes/ds28009.pdf
25  Using Arduino / Project Guidance / Re: CO Alarm on: November 15, 2012, 03:28:08 pm
Thanks Hazard ... that's why I said "I also have a relay that came with the horn. Can I just use a relay without and voltage coming back into the Arduino and frying it" in my first post... it's been ages since I've messed with electrical components but I do remember the purpose of a relay is to use a smaller current (and wiring) to send a signal to switch on a higher current. Just couldn't remember if the relay might have any kind of back flow to the board. So it's as simple as a pinout signal to the relay?
26  Using Arduino / Project Guidance / CO Alarm on: November 15, 2012, 03:07:14 pm
Hi guys... new to the forum and new to Arduino... ok I could have sworn I posted this around 3am but then I must be dreaming because for the life of me I can't find my post. I am trying to connect a motorcycle air horn (12 volts) to my Arduino so that when a carbon monoxide sensor variable exceeds a predefined level it sends an output signal to complete a 12v connection to the horn and sounds an alarm loud enough for the whole house to hear. I know I can't supply 12v from the board but can I use an H-Bridge I have to control a stepper motor (don't know the number off hand since I'm not at home at the moment). I also have a relay that came with the horn. Can I just use a relay without and voltage coming back into the Arduino and frying it or a combination of both? I'm sure I may need some resistors in there somewhere just not sure of the basic layout. Right now I haven't received the CO detector yet since it is coming from China and may get here some time next year lol ... however in the meantime I do have some photo resistors, pots etc to use as input devices to write the basic program. I will be glad to provide more specific information later when I have it available to me but if anyone can nudge me in the right direction working with the few items I have I would greatly appreciate it. Thank you!
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