hmmmm, i dunno. All I need is to see the chassis setup. can you guys take some pics please? kitsune, you know what I’m looking for mate, any space that can take nelly and her power/data wires….. let me know….
also, here’s some other crap/hype I’ve been investigating lately the use of the chip MAX628 to invert a pair of inputs, namely the pchan ones.
http://pdfserv.maxim-ic.com/en/ds/MAX626-TSC428.pdf
with this I should be able to hookup 4 nchan mosfets instead of the usual 2 nchan + 2 pchan mosfet setup for a motor h-bridge.
nchan mosfets (on average) have a lower “on resistance” than their pchan bretheren, given this I plan to make an even more efficient h-bridge and attain even more torque for that special motor of yours….lol…
in the prototype nelly deluxe I have used the LM317 variable voltage regulator with a resistor setup that limited Vout to 4.8V. That’s bit of an overkill but it was the only components I had on me at the time…..
Now I’m using just a standard 5v regulator, like this one FAN1117A
http://www.fairchildsemi.com/ds/FA/FAN1117A.pdf
it’s a small pkg that helps keep everything compact but still can source up to 1A if needed. from my own measurements I’ve found that the RX and Steering Servo parts don’t drain more than 250 – 300mA, Easily bellow the limit of the SOT-223 package.
one last thing I’m investigating is incorporating a li-poly overdischarge protection circuit based on this chip: UCC3911
http://focus.ti.com/lit/ds/symlink/ucc3911-1.pdf
the goal is to rig up the rx to be inline with the UCC3911, when the chip senses the lipo’s voltage levels going under it can cut off the power.
the possible issue here is that if you hookup the lipoly protector INLINE (ie: in series) with nelly’s main drive circuit, you’re adding another level of loss and inefficiency to the circuit.
so I thought, I might as well make the UC3911 operate like the power switch on a mini-z chassis, which is to only switch the power off from the RX circuit. the motor mosfets are not part of that circuit and are directly connected to the battery, this way there is less loss and I don’t have to worry about a small SO-16 packaged chip to take up to 8A!!
end rant..
cheers,
ph2t.
