Bare bones project board
Ugha
Posts: 543
Does anyone have a schematic for a "bare bones" project board for the BS2?
Or a link to one?
Meaning it'll have power regulation and reset control, but no programming capabilities (I can program the BS2
in a BOE then put it in the project board).
·
Or a link to one?
Meaning it'll have power regulation and reset control, but no programming capabilities (I can program the BS2
in a BOE then put it in the project board).
·
Comments
Mike's right; the Super Carrier is a great place to start from.
A couple of things to consider; if you're going to experiment with more than one Stamp, put a ZIF (zero insertion force) socket on it. It will definitely save wear and tear on the Stamps and the socket! Add a servo socket (with provision for separate servo power), put an experimenter's board in the prototyping area, and it's a pretty good board!
Regards,
Terry
You may also want to try the BS2 OEM kit. For $31.00 it is a deal.
http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/ProductID/21/List/1/Default.aspx?SortField=ProductName,ProductName
SJW
See attachment
My main problem is understanding... Before I saw your layout I made up an image of what
I THINK is absolutely required for a BS2 project board, and I think I understand it, but I'd
still like to run both the schematic, and my understanding of it, past you guys who actually
know what your doing [noparse]:)[/noparse]
This is based on the schematics for the carrier board, the super carrier board and me staring
at my BOE for an hour straight.
C1 = 47uF
C2 = 1.0uF
VR1 = Almost any 5V regulator (Am I wrong in that?)
IC1 = Any 24pin Basic Stamp (Mainly BS2)
S1 = Momentary On switch for reset
From what I understand, Sout, Sin and ATN are only needed during the programming
process and aren't needed for operation. Do they need to be grounded?
Also from what I've read, the RES pin must be pulled LOW in order for the BS to reset.
From what I can tell, the Carrier board used the Stamp's on-board regulator to convert
the power to 5v, and the BOE and Super Carrier have their own regulators so Vin isn't
needed... I'd assume not using the on-board regulator is a better, safer solution.
I *Think* C1 and C2 are for "smoothing"... but what I don't understand is why the BOE
uses 1000uF capacitors instead of the 47uF and 1.0uF of the Super Carrier board. Does
it matter?
Should C1 and/or C2 be electrolytic or does it matter?
Thanks in advance for your help guys. And thanks to Mike for suggesting the Super Carrier Board
schematic as a starting place.
2) The 1000uF capacitor is for filtering the power supply when you have high drain devices like servo motors. Different regulators require different minimum input and output capacitors. Unless there's a space issue, I'd go for the bigger capacitors. You do need a 0.1uF ceramic (probably 50V rating) at or very near the BS2 supply pins and preferably close to any other logic ICs on the board.
3) If you're just using the Stamp and the stuff it controls doesn't draw more than perhaps 20-25ma, you can use the regulator on the Stamp module. Otherwise, use an external regulator. The LM7805 is cheap and reliable, but it requires a supply voltage about 2.5V higher than that needed by the output circuitry (5V). The rest gets turned into heat. To save power, use a "low dropout" regulator like those that Parallax normally uses, for example on the BOE.
4) Sout, Sin, and ATN are used for programming. If you're not using them, connect a 10K or higher pullup resistor between Sin and +5V and between ATN and +5V. You normally should not leave unused inputs "floating". That increases the power drain.
A couple questions:
The 0.1uF ceramic near the BS2 supply pins... Would that be breaching Vdd and Vss next to the stamp?
This is to smooth out the power so the ICs don't receive false HIGHs, right? (I want to make sure I actually
LEARN this stuff)
Would you need a heat sink on the LM7805 with a 9v battery as the supply?
Thanks for the info on input pins... do I need to worry about output pins at all?
take a look at it and see if this one is a little better?
Excuse how I crammed the changes into the old schematic, I wanted to make sure I
understood what Mike said correctly before I redrew it from scratch.
C1 = 1000uF Electrolytic
C2 = 1000uF Electrolytic
C3 = 0.1uF 50v ceramic
R1 = 10K ohm 1/4watt
R2·= 10K ohm 1/4watt
VR1 =·LM2940CT-5.0·/w heatsink
IC1 = Any 24pin Basic Stamp (Mainly BS2)
S1 = Momentary On switch for reset
I'm not fully understanding what the datasheet for the LM2940CT means by ESR is
critical. I understand that normal Electrolytics on average have an ESR of 1-7 at
100uF, but I have no idea, other than looking at the capacitor's datasheet (which
are few and far between on the parallax site) how to check. Would it be as simple
as hooking it up to my multimeter and measuring the resistance? Or does the current
play a role in ESR rating?
I’m not Mike Green, but I will address your connections to SIN and ATN. You don’t want those pins connected if you’re not using them. They are internally pulled where they need to be. By adding external resistors you could actually cause conflicts…The ATN line is internally pulled down, but you’re trying to pull it up. If your resistor was a low enough value you could succeed in holding the BASIC Stamp in a reset state. SIN is also pulled down. A low enough resistor value there could cause the Stamp to sit in a break condition (effectively locked up). I would recommend removing them.
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Chris Savage
Parallax Tech Support
So I don't need to worry about what Mike said about the inputs floating, because they aren't floating, they have internal
resistors that handle that problem? Or something like that anyways.
Hey Chris... how come there isn't more info on the smaller components you guys sell on the website? I don't mind
buying everything through Parallax (I learnt my lesson with an LCD problem) but I'd like more info.
Is there a place to get datasheets or something for stuff like the capacitors you sell, or the 10k digital pots?
I know this isn't your department, but can you pass it along?
Floating inputs usually refers to unconnected I/O pins. These can oscillate in a design and cause small ripples/noise in the supply and can also cause a slight increase in current consumption. The noise/ripples are usually filtered by bypass caps in the circuit and the extra current can be cured by simply setting the unused I/O pins to output low, although it’s not usually a problem to leave them floating. Like I said, in battery powered systems every uA counts and so you’d want to do something there for that reason only. Take care.
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Chris Savage
Parallax Tech Support