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May 16, 2008
Technologist, programmer, etc.
University of Texas at Dallas
Tutorial - TB6612FNG Hookup Guide
about a year ago
I was wondering the same thing. The datasheet refers to dead time when switching modes under "H-SW Operating Description " and shows a waveform indicating this dead time exists at the rise and fall of the output PWM. If this happens using the internal diodes, then I think we're safe. To confirm here's what I did:
I guess the built-in protection diodes provide at least some level of protection; although, I'm not sure how robust they are. Note that my observations were using a single motor - using two motors may change the results. It might be a good idea to switch to "stop" or "braking" mode before reversing directions, and I guess it's a good idea to keep an eye on temperatures for long-duration or high output rides.
Tutorial - Transistors
about 5 years ago
I think this sentence is confusing: "A PNP works in a same but opposite fashion. The base still controls current flow, but that current flows in the opposite direction – from emitter to collector."
Looking at the previous paragraph: "The NPN transistor is designed to pass electrons from the emitter to the collector (so conventional current flows from collector to emitter)."
about 7 years ago
After measuring the resistor and getting something in the 350Ohm range, I tried resoldering, then replaced with a new resistor altogether, and eventually came to the conclusion it's probably the MOSFET. I got the same resistance with both resistors, and my multimeter jumped all over before it finally gave a reading every time I tested. I'm going to try a new MOSFET tomorrow. Thanks for your help l0gik!
Here's the solenoid we purchased: http://www.ebay.com/itm/3-8-Electric-Solenoid-Valve-NSF61-Potable-Water-12VDC-24VDC-VAC-110-120VAC-G28E-/290791658142?pt=LH_DefaultDomain_0&var=&hash=item43b488929e (12VDC, 500mA).
I have this and the corresponding breakout board connected to a 12V solenoid (which is connected to a beer line) and a GPIO pin of a Raspberry Pi (powered by the 5V side of the same molex connection powering the solenoid). The Pi outputs 5V for a specific period, then drops to a few mV. The solenoid opens just fine, and the beer flows great (nice head), but it doesn't ever close. It's great for getting drunk, but kind of ruins the project.
I measured voltage across the solenoid terminals, and it goes right to 12VDC, but never drops below 5VDC. I think the pressurized system combined with a relatively high "low" voltage (5VDC) is preventing the valve from closing. Any ideas how to get it closer to 0V when the Pi's pin is low?
News - Your Personal Black Box
about 9 years ago
Props for the Vannevar mention!
about 9 years ago
What kind of t-shirt is this printed on? I'm kind of between sizes, and I want to look super swanky in a custom enclosure.
Tutorial - WiFly Wireless SpeakJet Server
about 9 years ago
about 10 years ago
Yeah, the chisel or bevel would be nice.
News - Snappy Cluster
about 11 years ago
Friggin awesome work guys! You're my hero's.