Shutting down the stamp AND power?

shandar

Hi there!

Does anyone know if it is possible to turn of the stamp as in END and turning of all power outputs, such as the normal pins, vss & vin? Or is the only way to disconnect the battery? I'm using a HomeWorkboard btw.

Just for the fun of it I'm trying to build my own little "intelligent" room using a basic stamp and my computer. Since I started yesterday I haven't got very far except for building a remotecontrolled lightswitch. Using a servo the stamp moves the dimmer to the desired lightlevel. I decided to add a button that turns the light off and and turns off the stamp, but it seems like the servo still draws power even if the stamp is off and the servo isn't moving.
I turned the light of this way yesterday when I went to bead and when I woke up this morning the battery was completly dead. I know that the stamp draws power as long as the battery is connected, but it is something like 7 ua so it should be able to drain a battery all on its own...

Any ideas?

/Mikael

K de Jong

Well, you could use a swith to turn off all the power if you go to bed. Then you will need an external power supply (wall wart) for your Stamp to be able to switch it off.

A next step could be a relais of some kind. Then you can have the Stamp switching of after a while. Problem will be to switch on again

Regards,

Klaus

Chris Savage

A quick observation would be that if you're trying to build an "intelligent room", you won't get far if the computer is "shut down".· However, I would recommend powering the board from a Wall-Wart instead of the battery to solve your problem.· Especially if you are running a servo from the same supply.

To address your question though, the circuit I have used in the past to kill power was to power a DC circuit through an SCR.· The circuit would flow through the NC contacts of a DIP Relay.· When you want to shut the system down automatically, you energize the relay (Through a resistor/transistor combo) and that opens the contacts temporarily killing power, which releases the SCR.

Of course, I haven't used this circuit in a LONG time, probably back when I was learning as you are, and there may be better ways, however, this one works in a pinch.· I would still just recommend a Wall-Wart.


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Chris Savage

Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777

Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
·

Gadgetman

I would add is that you might consider a recharge and control IC which can recharge batteries and automatically switch to battery power if the mains fails.
Servos and other power-hungry systems could be fed via FET transistors or 'power management' IC's (3 to 8 decoders, really, but which are able to deliver a lot more power on the outputs)

K de Jong

I think the idea of a wall wart is a good one for more lengthy experiments.

But there are many types of wall warts and I just don't know which kind would fit best to the HomeWorkboard.

Klaus

shandar

Yeah, I know I wont get very far if the basic stamp or main computer shuts down, but that will be a later problem. First of all I'd like to get things working. But I was thinking, isn't it possible to cut the power to the servo using a simple transistor? By putting a transistor between VIN and the servo and then controlling it from the stamp I should be able to cut the power usage pretty quick..? When I want to use the servo I make the transistor go high, thus letting current flow through the servo, move the servo, and then make the transistor go low again..?

Of course, a wallwart is the best solution, but then I have to get outside and walk all the way to the closest electronics-store.. I'm too lazy for that :P

I'm not *that* good (read: useless :P) at electronics , so please correct me if I'm wrong... [noparse]:)[/noparse]

Post Edited (shandar) : 8/28/2004 9:44:12 PM GMT

Chris Savage

Yes, you could use a transistor to switch the Servo in/out, however, you will need one that can handle the current the servo draws MAX.



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Chris Savage

Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777

Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
·

Beau Schwabe

In a former life, many of our projects did not have the luxury of being "plugged in", we had to completely rely on
battery power so it has always been a big advantage to consider power saving schemes. With that said, the typical
procedure is to design for functionality first....In other words get the project working past concept!!! Then take a
step back and look at how things are hooked up and how they interact with one another. If you can reduce the
current supplies to a point where they will still meet the current demands when everything is said and done, then by
all means take appropriate measures do so. One project in particular we were faced with would only run on a 9V
battery for 5 hours continuous. After applying rigorus power reducing techniques we were able to achieve 3 months
of continuous operation from a 9V battery. I would much rather pay for 4 batteries in the course of one year, than
to pay for more than 1600 over the same time frame.

I happen to be working on a similar project at home (more details later) which also involves using a hobby servo.
...And like your project, the servo only needs to be moved on occasion to one position or the other with no additional
position updates. Because of this special case project, I have adopted a method to Enable / Disable a 5 Volt regulator
that supplies power to the servo and other components only when things need to be updated. When the regulator shuts
down, the STAMP for the most part goes to sleep periodically checking a series of inputs to determine if it should
wakeup other parts of the circuit or simply hit the snooze. Depending on what STAMP module you have, will determine
how much current the stamp will consume in sleep mode.

Here is a circuit that might help you to get started... Now granted, you can buy a 4-terminal voltage regulator off
the shelf that already has an enable or select line, so you might want to go that route. From a personal point of
view, if I don't use PARTS that I already have lying around the workshop, then pretty soon I won't be able see out
of the workshop (which is closer to the truth anyway - grin) Anyway, the "front end" of this schematic is basically
what you would find inside of a 4-terminal regulator.

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Beau Schwabe - Mask Designer III

National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071

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