choosing relay

I want try and build this: http://davehacks.troublem8ker.com/wordpress/?p=99 I'm having some trouble finding an appropriate relay, though. I also posted a comment on his blog, but I don't know if he still checks that. Here's what I posted on his site: "I’m going to try and build this soon soon, but had a couple of questions. I don’t know if you still check these comments or not, but here’s hoping.

1. Do you have a link or some information on the relays that you used? I think the optoisolators you used have been discontinued, and you said you were worried about the voltage through them anyway. I’m trying to find a good low-current relay to use. I have a general idea of what I need, but if you could help me out with something specific, that would be great.

2. If I just omit the automotive relay from the circuit, I should be able to retain the ability to turn off the car via the cell phone, right? I will be trying to find a cheap Android phone to use, so I should be able to control the number of pulses it sends, so I’m not terribly worried about it turning off with extra pulses right after it’s turned on.

Thanks!" Really, the first thing I need to do is make sure the vibrate motor on the phone that I use will output roughly the same voltage that his did. But, for now, let's assume that it does. I understand basic stuff about electronics, but the stuff contained in data sheets just make my head spin. From my limited understanding, I think this will work, but I'm not positive. http://www.mouser.com/ProductDetail/Avago-Technologies/ASSR-1511-001E/?qs=sGAEpiMZZMuXU54bFMy7bNoWTYww4RAhtxi4Bk0SmaQ%3d Any help is appreciated. However, please don't suggest one of the commercial products. I'm not trying to spend several hundred dollars on this. I'd rather go without than spend that much money on a commercial product then have to pay for the service on top of that. If I can make this work, then great. If not, then no big deal.

So if I dial that number, I kill your car engine? Or if it starts, it will start in gear, or when the engine is already running?

Remote start systems are deactivated when the key is in the ignition, so you wouldn't kill it. I don't have a manual transmission, so starting in gear isn't a problem. The reason I want to use an Android phone is because with a little creative use of Tasker, I should be able to actually limit the phone to only give out pulses (vibrate) when I text it with a certain keyword. Even without Tasker, there are apps that can block and/or whitelist numbers, apps that can utilize different vibrate patterns for different contacts, etc. Basically, I'm not terribly worried about the security aspects.

The the second question - why? Why use a phone for an app that is far better suited to a remote? (And usually cheaper to use and more reliable.) Nevertheless, assuming you have the required safety and other interlocks, the 12V relay choice is trivial. The relays must be rated for whatever current your IGN requires, and starter-motor. Though a typical 30A may suffice, I'd suggest a 40A or 60A rated relay. And you must be able to drive their coils, ie, supply whatever current they require to turn on. That's typically up to 250mA. You may only need SPST aka 4-pin or "on-off" relays unless needing DPST (Dual Pole on-off) or SPDT (Single-Pole changeover) or DPDT (Double-Pole changeover) - whatever is required for your vehicle etc. Click the "Relays" link up the top of this page or websearch for more relay info.    PS... Those optocouplers look ok. There are cheaper and more common types (eg, 4N28 and similar) but they may have lower rated outputs, eg, 50mA for the 4N25 to 4N28. But that's easily fixed with an extra transistor or FET (rather than replacing the opto if that should blow).

No remote can match the range of a phone. We're not talking about the same type of relay. I'm looking for a relay that needs to be soldered into the board, not an automotive relay. I already know which automotive relay I need (and I may just omit that altogether...see question 2 in my OP).

So how far away is your car when you start it; what range do you need? PS... Have a look at Jaycar's PCB Mount Relays, though equivalents should be available elsewhere...

The range varies. It can be outside my house, or a mile away. But that's irrelevant, really. I still don't think that's what I'm looking for. I'm looking for something very similar to the optoisolator in the blog, but like I said, that particular one seems to be discontinued (I can't find it anywhere).

It's a standard automotive Bosch/Tycho "cube" relay, any auto parts store. Very dangerous and probably illegal.... Starting in gear. Parking brake off. Hood open etc. etc. etc. I'm amazed the mods are allowing this. In fact it's a lot cheaper and of course safer to buy a remote start from say DEI, Compustar or Autopage then add one of their cellular modules.

Yeah... I think it's time I get to my point. The idea itself is IMO stupid. The design is IMO not good (from what I recall). Why use a mobile when remotes are available that do the same, and better, and LEGALLY with all required interlocks? Without an appropriate answer I had no intention of a detailed response (including design improvements). The distance and reason IS relevant. I know that Freak happens to be a terrorist and intends driving the vehicle into a kindergarten.... Or maybe not, but certain mods to vehicles are illegal for good reason. [ I'm kidding about the terroriser bit. And BTW, thanks Tommy, but IMO freak4dell was not harsh... ie, No worries freak4dell. Besides, I'm the terroriser (a term used by Bush in Harold & Kumar (Escape From Guantanamo Bay). ] Remote control via mobile phone has its uses, but rarely for car starting. Since cost was mentioned, viz:

freak4dell wrote: I'm not trying to spend several hundred dollars on this. I'd rather ...[not]...pay for the service on top of that.

Then why do this using a phone? But your first cost will be to install an approved push-button start system. The rest is about fitting the deign to the components available, not trying to source rare or expensive components to duplicate someone's design. And it isn't difficult to do that. Use your phone to monitor your home alarm system or mailbox instead.

Sigh...I guess I'll just have to figure it out on my own, or hope that the writer of the blog replies. It's pretty clear that howie II didn't read anything past the title of the blog. At the end of the day this has no aspect of illegality to it. The only difference between this and just buying a 2nd remote and programming it to work with the remote starter is that the remote doesn't have anywhere near the range that a cell network has. I would just be left with two remotes that only activate at 300-400 feet at that point, which is twice as useless as the one remote that I already have that does exactly that. This has nothing to do with push start (which would actually be quite a bit more unsafe than anything else mentioned in this thread, considering I'd have to disable my mechanical steering wheel lock to accomplish that). The distance is indeed irrelevant. My reason is moreso because I was never a fan of carrying a second remote in the first place (I have one of those flipkeys with the car remote integrated), and I've grown tired of carrying the second remote just for the function of starting the car. My cell phone, on the other hand, is ALWAYS with me, and if it can function as a remote for my remote starter, then that's awesome. As far as cost, a full Viper SmartStart system costs $400, and the service costs $50 a year. My current remote start system cost me less than $75, a cheap Android phone can be picked up for $50ish (less if I don't do a smartphone, or free if I use one of the half-dozen or so phones I have lying around at home already), and a few bucks of prepaid service can last months, or adding an extra line to my existing plan costs $5 a month. That actually ends up being more than the Viper service, but considering I spend a majority of my time abroad and away from my car, I could simply just disconnect the service for most of the year, meaning my yearly cost would be whatever I needed it to be, rather than being forced to pay upfront for a year. Then there's the fact that a system operated based on calls and texts doesn't require that my phone have a data plan, whereas the Viper system does. Yeah, that was harsh, so feel free to ban me. It doesn't seem like I'll be missing much, anyway. I figured this would be a good resource, since the original author of that blog found help here with no issues, but I guess I was mistaken.