just an idea there andrew.

why not design it so the flipper is the self righter. hence u kill two birds with one stone. u have a weopon and a self righting mechanism

thats how most if not all flipper bots do it.
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Andrew Welch, Team Unconventional Robotics

yeah, but I don't like doing things the way sensible people do it

The way my flipper works it may have some self righting properties, but I expect it will only work in some situations. I want a bit more flexibility, and have the bits to do a separate self righter, so I'll give it a go

I might also be able to use the self righters as a secondary weapon or active shield.
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The Engine Whisperer - fixer of things

I've been doing some serious work on my car for the last couple of days (trying out a new engine configuration), so I haven't had that much time for robot building, but today I picked up a long bolt for the flipper pivot, drilled the holes, and put it together.

The flipper moves really nicely, and the whole thing is very strong, but I'm not 100% sure on the flipper geometry yet.
Basically the ram is a bit longer than I need, but I don't have to use it's full throw if that's a problem.
My main concern is that as the flipper extends there's more and more leverage against the ram, so the lifting power will decrease.
That was always part of the plan though, because as the flipper activates it will have maximum power at the bottom of the stroke, with the power dropping off but the speed increasing as it lifts.

Hopefully that will get it to throw things pretty well, but if there's not enough power in the ram it might not get enough speed up.

Ahh well, only one way to find out

If it's not good enough I have the fatter, shorter ram to try, which would improve the geometry as well as having more power.
The downside to that is slower action, and more gas / air used for each flip.
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The Engine Whisperer - fixer of things

Well, not much physical robot work has been happening, but I did fix my air compressor using the pump out of the air conditioner we found on the last build day

I've also been working on some FET boards for speed and weapon controls.

Having access to a PCB prototyping machine like this helps:
http://robowars.org/forum/album_pic.php?pic_id=561

Here's the first version of my Opto isolated H-Bridge board for motor control:
http://robowars.org/forum/album_pic.php?pic_id=564
PCB with a light shining through it:
http://robowars.org/forum/album_pic.php?pic_id=565

And this is a 3 phase motor driver board, which may see use in a future "Plan" bot:
http://robowars.org/forum/album_pic.php?pic_id=566
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The Engine Whisperer - fixer of things

and how much are they going for
lol
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as a shadow is seen and not heard i am here
-Waddy the phoenix

Nice Work on the design layup of your board there.. but I had a look at the specs of the FETs you are using, and they look a little under-rated to me..
(Assuming you plan to drive Drill Motors or something similair)

The maximum drain current spec on the front of FET datasheets isnt a real spec in the sense that you cant drag that amount of current through the fet consistently. its kind of like a PMPO rating for speakers unfortunatly.

There are some good notes on how to figure out what a particular fet will *realistically* carry here.. http://www.mcmanis.com/chuck/robotics/projects/esc2/FET-power.html

But in brief, those Fets look like they will only take 5 amps at 24v or 10 amps at 12v, and thats assuming you have a nice heatsink, which your board doesnt.. If you look at Figure 14 on the Fet Spec sheet you will see what I mean.

They have an Rds(on) spec of 25mOhms which is *5x* more resistance than the IRF1405 fets we use in the IBC. Without a heatsink and with 5x the resistance, I would guess you will be looking at about 1/10th the power handling capability..

You might get away with running Scooter motors maybe, since they use a lot less current than drills.. I think with Drills or similair, you're going to be seeing some smoke the moment you have to give something a bit of a push and load them up..

I'd look at some beefier FETs if I were you..
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Great minds discuss ideas. Average minds discuss events. Small minds discuss people

Found the datasheet (it's at work normally). Yeah they're not going to handle amazing current, but they let me test out the design and then decide on what I need.
The nicect feature of these though is that I can get lots of them for free

There are also a few tricks in the board design. One is that I can easily expand the board to run parallel FETs, and the other is that all components are on the same side, with nothing on the back of the board. This means that the whole thing can be clamped against a large alloy heatsink, or even a structural alloy chassis plate, saving weight and space.

So far I'm going to be using a single scooter motor, which won't be excessively loaded.
If I have problems though I'll shell out for some higher current FETs and modify the design if necessary.

The main aspect of this design though are:

modularity - each board will do one task, and be easily changeable
toughness - everything is isolated, and all FETs have overvoltage protection on the gate drive (in case they're used on much higher battery voltage)
simplicity - parts are easily replaceable and construction is quick
scalability - it's easy to add to the overall design to drive different things


I'm doing some smaller weapon control boards as well, and someone I work with has a microprocessor receiver / channel decoder / PWM driver board pretty much sorted, so soon I'll have a configurable full control system that's very easy and cheap to use.
Want one motor drive, steering, and 4 weapon outputs? Easy, just plug in the right boards. Want mixed tank control, a variable speed weapon, and a single output srimec? easy!

The trick now is to get it all working
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The Engine Whisperer - fixer of things

The flipper mechanism is now working, and at 100psi I managed to dent the frame by throwing a brick in the air

It came down and left a dent!
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The Engine Whisperer - fixer of things