5v regulator connection on BOE

Toborg

Hello,

I am a newbie here and have a simple question. From what I have read supply voltage going into vin of·the bs2 needs to be a·regulated 5v. I am trying to replicate the Board of education regulator circuit in a smaller package for a project. From the schematic of the serial board of education it looks like the vin from the battery goes straight in to the vin of the bs2, before the 5v regulator.·Is that correct? ·I know this is probably a silly question, but I wanted to make sure that I did not damage my stamp. I have attached the schematic. Any assistance would be great.

Chris Savage

There are 2 voltage pins on the BASIC Stamp, Vin and Vdd.· Vin can handle 5.5 volts to 15 volts on the BASIC Stamp 2.· Vdd would require a regulated 5 volts if you used that.· You wouldn't use these both at the same time.· This link should help explain it.

http://www.parallax.com/html_pages/tech/faqs/fctl_info.asp#VIN%20Pin%20use

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Chris Savage
Parallax Tech Support
csavage@parallax.com

allanlane5

Actually, the BS2 has an on-board regulator. It gets its input from Vin, and outputs on Vdd. It's good for about 100 mA max -- 50 mA would be better, and the BS2 hardware takes about 5 mA.

So, if all you need is another 40 mA or so, you can use the on-BS2 voltage regulator.

If you decide to have an external regulator (which is a good idea, by the way) then you feed the output of the external regulator to Vdd of the BS2, and leave Vin disconnected.

In either case, make sure the 'ground' line is connected to Vss. Vss is the 'ground' for the BS2, regulators, and signal ground for the SERIN/SEROUT/DEBUG signals.

Jon Williams

I don't recommend using the onboard regulator for external circuits; a very simple accident could cause a problem that will require a big fix to your expensive BASIC Stamp. A few years ago I ignored my own advice, crossed up some wires, and watch my BS2 regulator unsolder itself and slide off the module!

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Jon Williams
Applications Engineer, Parallax

Chris Savage

To clarify on your original post, if you already have a regulated 5 volts, that can be fed directly into the Vdd pin on the BASIC Stamp, bypassing the internal regulator.· Also, your external regulator could power any other 5 volt devices you have, since, as Jon stated, you shouldn't use the on-board regulator since you've only got about 45 mA of current available from it.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Toborg

Wow, Thanks for all the replys. All of the information was extremely helpful. Any suggestions for external 5v regulators?
I have purchased the one that is in the schematic for the BOE, are there others that are better?

Chris Savage

Better is a subjective term...It also applies to the application.· The regulator we use if perfect for most applications involving the BASIC Stamp and much of the typical components connected to it.· It's a low dropout type, and can supply up to 1A with adequate heat sinking.· If you need more current, you'll need a beffier supply.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

LoopyByteloose

First, get a low drop out regulator if you are using battery. These work done to 5.5 rather than 7.0V. You will buy less batteries and carry less weight on a small robot.

Alternatively, get a low drop out switching regulator which wastes much less in the regulaton process [noparse][[/noparse]80% efficeient as compared to 70% efficeient.] Of course, if the switching regulator is not low drop out, it seems that the trade-offs offset each other. {i wish I could spell effic....????}

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Toborg

I have a LM2904 regulator. For the project that I am finnishing I plan to use a 9v battery to power the stamp 2. Only a few pins are used from the stamp to read an accelorometer and reset a pololu motor controller. I am powering the motor controller with a seperate source.
From what I have read, I think I need some capacitors in my regulator circuit. Is that true? If so how do I figure out what to use?
I took electronics tech in school 13yrs ago but never used it, I'm kinda blowin out the cobwebs. Any tips would be great, things have come along way since then.