Make:

Well, there is GOBS of 5 volts inside your computer, and USUALLY something that runs at 3 volts (2 C cells) will run okay at 5, but you'd have to tell us just what you want to stick in there before anyone can tell you if it will or won't work.

John

What is the voltage required? You could use a voltage regulator to get from 5V down to what, 3V? or around there.

It can be done and is quite easy... try some searches on google for it

For that matter, there's also a lot of power on the 3.3V output of an ATX supply, which would likely work well to power something expecting 2 C cells.

Except it's a little less convenient to tap than the 5V outputs. It's on the <a href=http://www.helpwithpcs.com/courses/power-supply-basics-inc-pinouts.htm>20 pin mobo connector</a>, so you have to splice in instead of use an available drive connector. Some PSUs also have a mostly-useless 6pin aux connector which have 2x +3.3V lines which you could easily hijack.

Using 5V, you'd only have ti find a dead cooling fan and cut the wires and connector off, using them to power the mystery device. Nice and clean.

John

I do this a lot for 5 and 12 volts. You can also put something between the 5 and 12 volt line and get 7 volts. to use that trick you can't ground anything. to get 3.3 volts, you need to cut into the ATX connector. I've also stolen 5 volts from the USB port.

Generally I'd try to figure out what the max limits of a particular 2 C cell circuit was and feed it 5 volts if it was 5v tolerant. If it really needs less voltage, you could drop a few volts with diodes in series.

Thanks for all the tips,

This is what i'm planning on putting inside the computer.

http://www.homedepot.com/prel80/HDUS/EN_US/diy_main/pg_diy.jsp?CNTTYPE=PROD_META&CNTKEY=misc%2fsearchResults.jsp&BV_SessionID=@@@@1698905405.1151083829@@@@&BV_EngineID=cccdaddiedifjhhcgelceffdfgidgmj.0&MID=9876

This is my first project, and ofcouse I know I could use a USB remote, but why not a wireless door bell?

OK, so i've seen a few of the bases of these wireless door bells and some take 2 C Batteries. This is what I'm assuming.. but what if it only took one battery (1.5v). Would that be much different to get power from the PSU?

Where can I buy a voltage regulator? I'm going to my local home depot in a few minutes (to pick up this wireless door bell), so I'll check there.

I know the basics of electricity.. soldering.. that kind of stuff, but don't know a lot yet.. I'd really rather not slice the main 20-pin PSU connector. I prefer working with one of the smaller four-hole connectors.

I'm sure I have many more questions coming once I get started :).

Thanks again,
Brett

A couple months back I hacked a wireless doorbell into a remote camera shutter release, and it wasn't happy w/5V instead of 3V. But a different model might be OK with it.

If you don't want to cut the ATX connector (understandable) and your PSU doesn't have a 6 pin aux connector, then you're next easiest option is probably tap 5V with a few diodes in series (1N4001, for example). Common rectifier diodes usually drop around 0.6 to 1.2V (each).

A voltage regulator you'll find at an electronics store, and you've got a couple choices. First, and simplest, is a fixed linear regulator, such as a 78xx (where xx=voltage, ie: 7812 = 12v) but most electronics stores only stock the most common (7812, 7805, maybe 7806, 7808, 7809, 7815 or 7824 if it's very well stocked) and 3V output models are not considered "common". There is a 7833 which gives you 3.3V, but you're probably going to have to order that from Sparkfun, Mouser, Digikey, etc.

The second choice on voltage regulator is an adustable linear regulator like an LM317 (which can go down to as low as 1.2V, so it would work with even a 1 battery unit). You'll need a couple external components (resistors) to set the output voltage, so it gets a little more complicated. Google for more info. Also, if you're drawing more than a couple hundred mA with a linear votlage regulator (fixed or variable) it will want a heat sink. (but a wireless doorbell probably doesn't draw much at all)

I'd go for a few 1N4001 diodes off the 5V line, since you get 1N4001 for pennies at any elecronics stores (1N4004, 1N4007, etc. will all be fine for up to 1A).

Ok..
Before I even get to using the PSU power, I want to give it a try on battery power.
Is it possible to wire the positive and negative wires that originally lead to the speaker, to my two motherboard power prongs? So in effect this will be the same as pressing my power button. But, it seems that pressing the power button simply closes the circuit for these two prongs, for just a second. How could I simulate this with the wireless doorbell? Or would it be possible?

Thanks,
Brett

So help me understand ... the goal is to turn on and boot the PC using the wireless doorbell transmitter?

John

Once he gets this working, If we knew where Brett lived, we could go over and turn off his computer from the back yard.

A small relay will probably work here. PC on switches are momentary, and they pull a signal line to ground IIRC. So either a logic chip that is compatible with mobo and doorbell, or a relay will do the trick. Turning it off may actually be a problem, because the switch has to be pressed for a long time to turn off the computer.

Well, I'm guessing that an inexpensive RC doorbell uses a piezo speaker as opposed to a coil and striker, so there will need to be some sort of driver circuit added ... probably just a transistor. You could add a simple 555 circuit to stretch out the relay closure to allow turn off (presuming the PC doesn't act odd by holding the switch closed that long when you're turning it on).

Before I added this to -MY- computer, however, I'd let the unmodified doorbell sit on my desk for a week or two to make sure there isn't some other thing in the neighborhood that trips it. I would also place the unmodified doorbell inside my computer, close it all up, and make sure i can still ring the bell from around my house (wondering about the case shielding the RF signal, and the RFI from the computer swamping it).

John

Wait a minute ......

The original question was how to power the receiver from the PC supply ....

And the application is to turn the PC on and off ....

um .... if the PC is off, there isn't any power in the case to use.

Am I just not 'getting it'?

(the pico-current watching the on switch doesn't count, you can't load it down)

John

Haha :).

I didn't even think about that. How embarassing.
I'll just run it off the C batteries till I think of something else.
Thanks for pointing that out, though, John.

About the stimulating the power button. I don't care about the long hold down of hte power button.. don't worry about that. I have a program that intercepts the pressing of the power button, running any other program, or script, or shutting down.. etc.

So unterhausen suggested a "logic chip that is compatible with mobo and doorbell, or a relay will do the trick."

..again I'm not very familiar with electronics. Would I buy such a thing on mouser.com? And if so, i'm sure they have a million types of them, so what am I looking for?

Thanks,
Brett

jschuch, thats innacurate..... there are a couple lines that DO have some voltage on then, not high current, but maybe enough to drive what he wants. Most ALL motherboards require a little standby voltage/current to be able to operate the momentary switch that turns power on and off. The older PS's used a switch to the PS itself. THe newer ones have some lines that actually have small voltages

I knew that, but I doubted that they could source enough current to drive a relay, which would be the easiest way fo a novice to interface the doorbell to the PC. You're probably right that there is enough power to drive the receiver, and instead of a relay you could probably use some kind of FET interface to toggle the power.

But for a beginner, it would be easier to put rechargable batteries in the doorbell, and trickle-charge them when the PC is turned on.

John

Per the ATX spec, the 5V standby supply is guaranteed to be at least 10mA, and the motherboard should draw no more than 10mA in standby (for example, the real-time-clock). That's not much at all -- probably is too low for a relay.

However, the spec recommends 720mA as a minimum to support wake-on-lan and other advanced standby circuits. It's not uncommon to see 1-2A available standby current on modern ATX supplies. That's plenty of current for any 5V relay you're likely to use. Check the rating on the side of the PSU and what your system is currently drawing on standby before attempting.

But you still have to splice into the ATX motherboard connector to get at the standby power.

Batteries on wireless doorbells do tend to last many months, so it's probably simplest to just use a couple cheap batteries and forget about it. Disposable alkaline batteries work better for trickle drain, long term use like clocks and passive because they don't have as much self-discharge as rechargeables do. jschuch's suggestion of having the PC's power trickle charge rechargables would be a nice extra.

Hi,

Thanks for the suggestions.
I don't know where to get these relays.
Is this what you mean?
http://www.mouser.com/?Ne=300&handler=data.listcategory&Ntt=*relay*&terms=relay&crc=true&N=65507&Ns=SField

or this?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7625858904&category=78205

or maybe this one?
http://www.goldmine-elec-products.com/prodinfo.asp?number=G13988

Please advise.

Brett

Before you can buy a relay you need to make sure the receiver can drive one. Maybe you do know and it's just not in this thread.

Does the doorbell have a speaker, or a solenoid that hits a bell of some sort?

John

I've already taken it apart, but here is what the speaker looks like:

http://www.eportal.ws/doorbell/pic1.jpg
http://www.eportal.ws/doorbell/pic2.jpg
http://www.eportal.ws/doorbell/pic3.jpg

I guess its a speaker?

Thanks,
Brett

Well, (this is a -total guess- from your pictures) it appears that the COB module (Chip On Board) generates an audio signal of some sort, and that one transistor is probably a a simple audio amplifier to drive the speaker. If that is in fact correct, there are probably two options:

- you could add a simple little circuit that would take the audio signal and drive a relay.

- or, it -may- be possible to hack the components on the board to make that audio amp transistor actually drive a relay.

To do either, we'd need a little reverse engineering. So, I want to go buy the same unit that you have. This isn't really altruism, I've been wanting to me able to turn on some floodlights in front of my house from my car. I've been watching for a good deal on an old garage-door remote, but this actually looks like a cleaner (physically smaller) solution.

I could never get your link above to work so I searched Home Depot and found what appears to be the one you bought. Is your unit a "Heath Zenith Off-White Wireless Portable Doorbell ( Model SL6150 )?

John

Yes, that is the correct model. Let me know what you find out!

Thanks,
Brett

Cool, I'll be driving right past a home depot this afternoon.

John

Did you get a chance to take it apart last night?

Brett

Hey Brett,

Drop me an a note so that I can send you an email.

hbws (at) hackersbench.com

John

Man, pulling a thread out of the past....

This would work even better for your remote controlled PC ....
<BR><CENTER>
<a href="http://www.kqzyfj.com/click-2448011-10439518?url=http%3A%2F%2Fwww.geeks.com%2Fdetails.asp%3FInvtId%3DRM01&cm_mmc=CJ-_-2085188-_-2448011-_-Logisys%20RM01%20Remote%20Control%20Molex%20Connector%20Kit&cjsku=RM01" target="_blank"><img src="http://www.geeks.com/imageshare/R/150x150/RM01-unit.gif" border="0" alt="Logisys RM01 Remote Control Molex Connector Kit"/></a>
<img src="http://www.tqlkg.com/image-2448011-10439518" width="1" height="1" border="0"/>
</CENTER>
It looks like it was made as a car add-on of some sort, but since the remotes have two buttons, and the receiver only has one output, I don't know what it might have been intented to do. I'm guessing one button activates the output, and the other button turns it off, but I don't know.

Geeks.com is clearing them out for $11, which is a bit less than the doorbell cost.

John