How Much BS2 Module Current Available at Vdd?

Bill Chennault

All--

I would like to power an eb501 off a BS2 Vdd. I was under the impression (mistaken?) that the eb501 drew 2 amps. However, when I read the "Product Brief" it says all it needs is 34ma at 5vdc. This is confusing to me. I know I can safely draw 34ma out of·Vdd.·Is it possible to drive the eb501 safely off a BS2 module's Vdd pin?

Thanks!

--Bill

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Mike Green

Bill,
The Vdd pin on a BS2 module that's powered from Vin comes out of the +5V regulator. The regulator will protect itself from overloads. The worst that can happen is that the BS2 regulator will shut down and refuse to power the Stamp or anything else while an attempt is made to overload it.

General advice: Vin should be kept as close to 6V as you can (don't try to run the Stamp off a 9V battery) to minimize heat dissipation. 6V is enough above 5V to provide well regulated power to the Stamp and other logic. I don't know what the EB501 draws, but 34mA sounds reasonable. The Stamp module itself draws under 10mA if I remember correctly. That's still under 50mA total which is the official limit for the regulator.

Bill Chennault

Mike--

Thank you for answering my simpleton question.

I plan to develop an interface and simple code to drive Ugly Buster remotely via the eb501 and a Class I Bluetooth dongle, which I understand will provide more range than the "other" (?) Bluetooth device. It will be a poor man's R/C. However, if I can make it work, then it should be fairly easy to make it available across the net.

Additionally, Ugly Buster's larger cousin is in the advanced planning stage. He will cut my grass via the control system I hope to develop with a Bluetooth apparatus similar to that on Ugly Buster. I am thinking all 12vdc, with two gear motors on two drive wheels and one gear motor with a chain to turn the front wheels. Actual grass cutting will take place at about 1k RPM at whatever experimentation tells me is the right blade length. I am thinking they will have to be about 6" long and I will have four of them for a total cut of 24".

I hope to put a web cam on the machine so I can sit in my lounge chair, control the device via a joystick, and watch it on my big screen above the fireplace while I'm sucking down a longneck. Maybe Mrs. ringlord will rub my shoulders as I'm working.

Any thoughts from you or anyone else would be appreciated.

--Bill

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You are what you write.

Mike Green

Don't forget various kinds of failsafes. You're talking about a dangerous machine. You need for the whole thing to shutdown if there's a failure of the remote control link, whether the signal fails or the data coming across looks unreasonable. Some Bluetooth devices have a signal level output. That should be used to shut it all down if the signal disappears. There should probably be a watchdog timer on the controller. If it doesn't reset an external timer every so often, the whole thing needs to be shutdown until manually (hands on) reset.

Bill Chennault

Mike--

Thank you very much for the cautions.

I have been thinking of failsafes since I began thinking of the project; they have to be positive and totally reliable.

--Bill

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You are what you write.