For simple PWM control you can get away with using just a logic level power MOSFET <http://www.moodle2.tfe.umu.se/pluginfile.php/45884/mod_resource/content/1/Infineon-2N06L07-datasheet.pdf> and two resistors for a total cost of less than $1 and no heatsink. For a real hack you can even eliminate the resistors. :) But to build it yourself with current reversing, the component count goes up to at least 6 and uses more expensive P channel MOSFETs. At that point you are better off with an IC but 4A will cost you more Alternately you could just use an RC brushed motor ESC.. A 3S (3 cell lipo = 12.6v rating) one *with reversing* should run you about $10 and then you only need one PWM output to control everything. I've never had an issue driving one of these directly from a beaglebone.
On Wednesday, November 1, 2017 at 1:50:13 PM UTC-4, John Morris wrote: > > [Putting this back on-list] > > On 11/01/2017 11:52 AM, Chris Albertson wrote: > > > > On Wed, Nov 1, 2017 at 8:40 AM, John Morris <[email protected] > <javascript:> > > <mailto:[email protected] <javascript:>>> wrote: > > > > On 11/01/2017 10:15 AM, Daren Schwenke wrote: > > > > When switching peltiers between heat/cool mode you can get some > > really high currents. > > > > > > I don't know much about it. This one is rated 48W/12V, so I used a > > cheapo L298N module, 2 channels at 2A/channel, wired together. (I'm > > not sure if that's allowed, but it seems to work.) Do you mean > > higher current than 4A? > > > > > > The L298N uses internal bipolar transistors. The device drops some > > volts and burns up a lot of energy in the process. I would go with any > > MOSFET based h-bridge rather then the L298. The298 has been obsolete > > for years. Ad will require a big heat sink and I think a fan. A > > modern device will not require a heat sink and not get hot. > > I picked that one because they're available cheap on a PCB with extra > circuitry marketed to the Arduino folks. It does come with a heatsink, > and it's near the Peltier fan in my box. > > I'm not married to the thing, though. If there's another solution > that's better and not much harder, let me know. There's a > VNH2SP30-based (datasheet [1]) "Monster Moto Shield", 30A MOSFET, for > example. > > [1]: http://www.st.com/resource/en/datasheet/cd00043711.pdf > > > I don't understand the use of Machine Kit for this. Everyone else > > builds these using a $1 micro controller. It is actually MUCH easier. > > This is the perfect project o use one of these $3 STM32 boards > > Perhaps this is just an exercise? > > The value IMO is in the demonstration of a full integration from > electronics to remote GUI, and in the overall simplicity for learners. > Maybe it's the lesson that comes after Alex's AND-Demo. > > I know enough about microcontrollers to know the basic control functions > could easily be done on an STM32 board, and there's probably enough > memory to do some logging, too. I'd believe if you said there's a good > way to build a network-connected remote interface and (maybe even > cross-platform) GUI, and $3 is a fantastic price point (the BB WiFi > adapter cost more than that). You're right, the value of this project > can't be judged by the efficiency of using Machinekit on a Beagle for a > thermostat. I still hope there's value in the lesson, and anyway, like > that guy in True Grit using a horse pistol to shoot rats, it's fun. > > Actually, this is really my first GUI ever, and my own eyes were > certainly opened. With haltalk and QtQuickVCP, the whole GUI took zero > lines of code outside the remote comp's ~dozen python lines to create > pins. Really amazing stuff. > > John > -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
