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Drawido Schematic and Description Errors
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Drawido Schematic and Description Errors

by adshea on Sun Apr 25, 2010 10:23 pm

I was just going over the Drawido page because I was interested in what you were using to run an oscillator at 1V and noticed some problems with the schematic and description.

First, the battery is backwards. There may be something I'm missing but the schematic on http://www.ladyada.net/make/drawdio/design.html shows the negative of the battery (short line) connected to VCC and the positive (long line) connected to ground. The polarity of the class A or class B amplifiers and the *555 or *551 chips is all with VCC>GND.

Second, the *555 (*551) is wired up as an astable multivibrator, not monostable. Monostable is a one shot that must be triggered, astable is the free-running oscillator.

Otherwise, great kit and great job bringing fun little electronics to the masses.

adshea
 
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Re: Drawido Schematic and Description Errors

by adafruit on Mon Apr 26, 2010 10:34 am

the circuit is hooked up as astable, please check it again :)

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Re: Drawido Schematic and Description Errors

by adshea on Mon Apr 26, 2010 10:59 am

I know it's astable. It's that the description says monostable.

One of the more popular ways that '555s are used is as a 'mono stable multivibrator' which is anothe way of saying an oscillator. The frequency of the oscillation is set by 2 resistors and a capacitor. The chip slowly feeds current into the capacitor until it is full and then, likewise, slowly drains it out. The resistors set how fast to fill and drain the capacitor and the size of the capacitor indicates how long it takes before it fills.


"Astable" doesn't appear anywhere on the page.

EDIT: I'm really not trying to be mean here and please don't take this the wrong way. I just remember trying to build things from descriptions in the Q/A sections of Electronics Now (I'm 23, yes I read Electronics Now) where the reply got things like this wrong and bashing my head against a wall.

adshea
 
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Re: Drawido Schematic and Description Errors

by adafruit on Mon Apr 26, 2010 12:02 pm

OK the typo is fixed

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Please be positive and constructive with your questions and comments.