Member Since: April 30, 2012

Country: United States

  • Yes, dougal is correct about 120V AC is the rms voltage.

    The power formula being used: power = Vrms*Irms only works if the load is resistive.

    I’m expecting in this case that the power factor is not 1. You would want to hook up a scope w/current probe to look at the phase angle between the voltage and current signals.

    I would be surprised if the power number on the bulb is not correct. I expect someone, even as a write this, is plugging some bulbs into a lamp socket, which is in turn plugged into one of those socket watt meters like the Kill A Watt, and verifying the numbers.

  • Heard from outside the trailer after Shawn’s gotten his next generation Redboard idea praised by Atmel: I haven’t had an orthodox career, and I’ve wanted more than anything to have your respect. The first time I didn’t feel it, but this time I feel it, and I can’t deny the fact that you like me, right now, you like me!

  • From

    Q: How do you pronounce MIPI? A: “mippee”.

  • Where’s the love for these transistor configurations? Don’t forget that opamps are merely multiple instantiations and variations of these transistor configurations (you’d need to add current mirrors, too).

    Common base? Useless? Look up cascode, a wicked great use of the common base.

    Emitter follower? Useless? What do you think is the transistor stage chosen for the output of many non rail-rail output stages? If you look at the size of a discrete transistor versus the size of a whole opamp, when you need more current output than the opamp can source, who you gonna call? Emitter follower, that’s who.

    The utility of these configurations is often seen by looking at the input and output impedances of the configuration:
    Low input impedances are typically driven with current sources, high input impedances are typically driven with voltage sources. Low output impedances make great voltage sources, high output impedances make great current sources. Then you can utilize feedback to accentuate good characteristics and suppress bad characteristics.

  • I’m in complete agreement. The setup for the story is complete nonsense.

    Good thing for SparkFun is if Nate ever gets lost or can’t fulfill his duties, a similar search for “Nate” on Digikey shows they have 79,780 Nate’s available. If even 10% of those are in stock, SparkFun can always get another Nate. (Well, if by Nate you mean some random RG178 coax cable that matches the search for Nate amongst all the other bogus Nate matches).

  • Excellent. I enjoy coming to pick up orders with my kids. Demos and exhibits will make them even more motivated to come along.

  • I hope the plan is to continue the option of “Local Pickup”?

  • Can the Simon board be used as an input to Scratch? Since children might often be introduced to electronics through the Simon game as a soldering project and it has the programming header, it would be neat to repurpose the board as an analog/digital input/output for Scratch. Anyone know how to do this?

  • These opamps are in an inverting configuration. Look at IC1A in the schematic. There is an input branch (C5 + R2) and feedback branch (C1 // R1). Think of these 2 branches as a teeter totter with the opamp’s - input as the fulcrum. You can do the analysis to confirm this analogy works. In any case, when the input is above the - input, the output of the opamp will be below the - input and vice-versa. The problem arises that the power supplies for this breakout board are defined to be VCC and GND. There is no negative voltage. This is a common situation in a digital world; there is often only +V and GND. Thus, for this circuit to work properly, the - input has to be kept somewhat above GND to give the teeter totter some room to operate. That is why the voltage dividers are on the + inputs; this raises the - input (opamp will try to set its output to bring the - input to the same voltage as the + input) up to the reference + input. It turns out for general applications, ½ VCC is a pretty good place to put the fulcrum as the teeter totter can swing in both directions.

    The 1uF caps on the inputs AC couple (or remove the DC from) the inputs. This allows the teeter totter fulcrum to be reset nicely for each stage. Otherwise, any DC difference between the input signal and the reference being applied at the + input will be amplified.

  • I don’t know if the supplier changed, but the plate is NOT Aluminum. A simple test with a magnet will verify…

No public wish lists :(