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Originally Posted by mswhin63
Another really really cool platform is the PSoc4 platform which as a brilliant IDE that is component based and I believe super easy to develop. I will consider this as a possible option after completing this semester.
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ARM seems to be the way to go for bigger stuff. I've heard good things about Propeller too. I'm not using Arduinos for this stuff though. In terms of efficiency they have worse to worry about than floats. Did you know digitalWrite(1,HIGH) takes 55 clock cycles to complete? PORTD |= _BV(1); takes 2 cycles. If you're familiar with the internal workings of AVR chips then the Arduino platform adds needless overhead. I will however be using an AVR of some description because they are cheap as chips and I have the tools here to program them.
Quote:
Originally Posted by rcheshire
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Oh I understand now! You're using it to control a TEC. For some reason I was still in dewstrap mode and was trying to figure out why on earth you're switching faster than about a couple of times per second. A telescope has an incredible amount of thermal mass so there's no reason to switch at a frequency above 1-2Hz.
That said a TEC should have considerable thermal mass so you shouldn't need to switch that fast. A few options are writing a subroutine with a series of delays, or using one of the pulse width modulators with a really slow clock cycle which can always be slowed down further by counting in a loop i.e. if (counter > 500) {change output and reset counter} else counter++; That can get you down to really slow frequencies
Looking at your circuit though you're running a MOSFET with 5V at the gate and 12V at the drain. To switch it on fully you need to be selective of your MOSFET. It could be you're never actually saturating the MOSFET if the Vgs threshold voltage of your chosen MOSFET is too high. This may cause a lot of heating. In your circuit for instance an IRF510 would dissipate 3W average, and an IRF1405 0.5W. You can verify this is happening by putting 5V at the gate (continuously) and measuring the voltage from Drain to Source. If it's not effective zero then you're not saturating the MOSFET and you're losing power across it. That MOSFET should not need a heatsink.