Well yes I was using a conservative worst case estimate for my old oversized linear satellite actuators And its worth mentioning that since I am using recycled fiberglass satellite dishes to concentrate the energy, they do need to point straight at the source of parallel rays For old style PV the controller could get a specific mode where it actually measures the power produced to optimize the positioning, actually I am hoping to investigate that soon, also in order to apply the same electronic infrastructure some day to an automatic wifi antenna tuning setup! And my WRT definitely does never use anywhere close to 30 Watts, as a matter of fact its powersupply is rated at 12W and I read somewhere that it doesn't even use half of it! Anyhow let me make clear that obviously the long run solution will be just a pic, an LCD and a few buttons or maybe some form of wired or wireless way of connecting it to the computer to monitor, fine tune and to do statistics... Its just that I don't have a pic programmer yet and I want a solution that I could even program with a friends programmer and then continue developing here... I have been impressed by programmers that I have seen that just seem to use two transistors and a few diodes (like this one for example: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=014&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=330146276296&rd=1&rd=1#nogoI may get one of these soon! Do you recommend it?) Is there such a published circuit that I could implement here quickly? >As for level conversions, I use a 74HC14 schmidt input inverter. >10k input resistor and clamp diode for the RS232 in side. Paralleled gates and 100 >ohm protection R on the out side. Good for 100's of feet. >Although given that you are far away, and up high (good lightning target), >I would use fiber optic cables for communication. And to save power, only >turn on the LED to send a SPACE condition (opposite of most logic). I like your suggested solution! is there a schematic you would be willing to share? How many optocouplers would I need to do also separate the computer side from the tracker side? Thanks for the collaboration! On 7/16/07, Robert Rolf wrote: > > Tobias Gogolin wrote: > > Besides I would estimate right now that tracking once across the range > takes > > a minute, at 24V 3A max that would be 72Wmin, so for any decent size of > PV > > 3A??? Just how big is this panel that you need such a power hungry motor? > DISeQC Satellite dish motors (rated to 1M dish size) draw about 300mA @18V > while moving and do H-H in about 90 seconds. > > > that would be worth to track you would recuperate the energy if the sun > came > > out for only a minute... > > Really? What is your loss due to angle error? > SIN (75), a 15 degree tracking error, is 0.97 or a 3% loss. Hardly seems > worth the trouble to move for less than a 20 degree error. > And then you have losses due to inertia (start surge) so it would probably > be more efficient to move for longer periods, but less often. > You can probably measure your motor/system and then model it to see what > minimum update time to use (10's of minutes I would think). > > And if you want to be really efficient, wait for a 15 degree track error, > then overshoot by 15 degrees so you activate the motor/PIC less often. > > > On the serial interface: what if I had a serial interface coming > straight > > from a not level converted source such as my WRT54G? > > That is a cheap little low power Linux Box that could even add remote > > monitoring capabilities to an installation! > > It's not THAT low powered. 30W or so. > A PIC would draw sub milliampers. e.g. microwatts, since it only needs to > do something a few times an hour. With a RTC (real time clock ) chip like > the Dallas 1302, it wouldn't need to have ANY communication since it > could compute everything from the current date/time. > And some flavours of the RTCs have 'alarm' outputs which you would program > to periodically wake up the PIC to do some work. (saving lots of power in > the > process). > > As for level conversions, I use a 74HC14 schmidt input inverter. > 10k input resistor and clamp diode for the RS232 in side. Paralleled gates > and 100 > ohm protection R on the out side. Good for 100's of feet. > Although given that you are far away, and up high (good lightning target), > I would use fiber optic cables for communication. And to save power, only > turn on the LED to send a SPACE condition (opposite of most logic). > > You can get the optical drivers from dead DVD players that have an optical > output. Lots to be found at the local eco recycle center. > > Robert > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- Tobias Gogolin cel. (646) 124 32 82 skype: moontogo messenger: usertogo@hotmail.com You develop an open source motor controller at http://groups.yahoo.com/group/GoBox -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist