The sabertooth 25 is probably a bit underpowered as well; with a pushybot like this you would be looking at some really large current bursts, particularly on the front wheels.

I just did a spot check on dollars per amp on some controllers, the results are a bit surprising:

Victor 884 $2.88 dollar / amp
Victor 883 $2.32
Victor 885 $1.49

Sabre 2x25 $2.50
Sabre 2x50 $2.50

IBC 2x50 $3.20

Sidewinder $2.49

I took the prices mostly off the RMP to keep the pricing as neutral as possible. The Sabretooth controllers are cheaper at the low end of the current range, while the Victor 885 has the most bang per buck at the high end. With the Victors, you have to factor in a BEC and mixer; this still only brings the 885 up to about $1.82 per amp (depending on your choice of parts).

With apologies to Brett, the IBC isn't looking like good value on this comparison, its soundly beaten by the 883 and the Sabre 50 - what's that all about???

With four motors and grippy wheels, I think the smallest controller would be the Victor 883 as its just a bit more capable than the Sabre 50 and has a bit better dollars per amp ratio. Since the controllers take up a similar amount of room, I can do a comparison table and let the builders pick what they want. I will probably stick in a set of Victor 885 controllers and graph the current with a data logger before suggesting the best economy an premium controllers.

The IBC is a higher "quality" device, it'll handle wildly varying input voltages without chucking a mental and it'll handle more volts than most of the smaller controllers.

That said with the batteries and voltages we run now its power supply stage is probably overkill.

Scorpions can be sourced locally keep in mind ;->

Would there be much interest in a "kit" build controller for this level of bot?
With the production levels in this type of controller, labor is a decent % of the sale price. If we make something based on the self protecting half bridge chips that the scorpion uses with an over voltage protection it could be done for ~$40-50 in parts with enough push for 2 drills.

We are hoping also to ramp up production of our wheels this year with the CnC mill etc a sales web page is not too far off.
_________________
Mechanical engineers build weapons, civil engineers build targets

does that figure in that you need 2 victors per bot compared to the 1 of the others

ibc also has the weapon outs which is handy unless your running brushless. thats another cost you need in a d switch or whatever
_________________
www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

I would REALLY like to see a keyed 1/2 shaft on those wheels - it would open up the Banebots and deWalt market for you.

The surface mount parts on the Scorpions are probably a bit much for new builders - worth thinking about though.

Part of this story is about using a methodical design process - I need to do some data logging to figure out what ESC and battery packs will work best.

@ Glen: true, I forgot about the 3rd channel I will factor that in next time.

I put the dual channel controllers in at their combined current rating, so the IBC was a 100A controller.

Well, the IBC is a 5+yo Australian made product, produced in small quantities by hand, so it was never going to be as price competitive on a simple per-amp basis as something like a Victor which is made by the thousands and most likely auto assembled.

It probably was $/amp competitive at the time I designed it though, If I recall Victors were much pricier back then. Plus of course, by taking RMP prices, you aren't including Import Duty and GST which would have to be paid when OS controllers are brought in, in any quanitity higher than 1 or 2.

Also, 2x Victors are not the whole combat robot story. To be as useful as an IBC, Add a Mixer board (remember the IBC was designed in the days when only $500+ radios had inbuilt mixing), a onboard *useful current* BEC, two weapon switches, associated mounting hardware and cables to the package and suddenly the Victors dont look so hot price wise.

And, as Jake pointed out, the IBC has about $40 worth of Switchmode regulator on board that most controllers dont have, allowing it to run off anything more than about 4v without dying. This was put in there because we wanted something for the small hobby/feather weight robots (actually The IBC was originally designed specifically to fit a certain space in Gary's first Shell Spinner (Flying Saucer - http://robowars.org/robots.html down the bottom of the page) and we knew we werent going to get 12+ Sub-Cs in there to get 12-15v (that most controllers need), so it had to be able to run from low voltages.

Plus of course, The IBC was based on the OSMC so we had access to the circuit diagrams and source code for easy local repairs by ourselves. Try fixing a blown up Victor or Sidewinder without a return trip to America in the deal.

And finally, the IBC and never-released MMC/BMCs were never actually designed for sale to others. I designed them for our own robots use, and reluctantly hassled Jason into building them for others when word got around and people kept asking about them.

So cost competitiveness on a per-amp bases wasnt ever a design factor. There was nothing like it available (the options at the time were Victors, Vantecs, OSMC's and that was it), we wanted it so we built it.

So lining it up on an amp-by-amp basis 5 years down the track is a bit outside of the original spec.

However, as you pointed out, Availability has been something of an issue recently since Jason started School part time and bought a house/got promoted to a Salaried (rather than a Wage) position.. which means he is working more hours, plus doing hours a week of school and just doesnt have as much time to make them as he used to.

If someone really wants one and puts the screws on him, you *can* still get them, he just did a rev of the circuit board with a few small improvements (mainly in ease of assembly area) and has a new batch underway, but the bulk of the sales go overseas, so neither he nor I are interested in making a lot of noise trying to push them here.

I'm keeping an eye on the slowly developing Silicon Carbide FET technology, which I think might cause a major revolution if they ever get out of the R&D vapor cloud. How about a Fet that can handle 1200v, 400 amps and survive at 500c ! If they make it to market I might be tempted to do an IBC3 one day..
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people

urethane wheels for dewalts wood be good. specially in super thick widths.

the table looks good for a magazine, victors have gotten heaps cheaper looking at RMP just now. thats pretty good! IBC is pretty expensive at rpm tho. $320US. there only $310aud here i think that again would probbaly bring it in line with the others

4 drills or equivalent though i think the best you could do would be victors cost wise. gets my stamp of approval as the most reliable controller thus far pretty universal too in that there still pretty small by standards and can use them in much bigger projects later. next thing is the sidewinder which is way more spensive.

edit - whups just got post blocked by brett heehee
_________________
www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz

is it just me or is the RS80D starting to look like a very good high amp controller?
80A per drive (same as sidewinder) and over $100USD cheaper than the sidewinder
its got me thinking...
_________________
http://au.youtube.com/user/crustydemonsully

The day I stop giving 100%, is the day I stop competing

It looks good on paper but every user I know hates it! They have a very complex and large PCB and when they break, they are next to impossible to fix. They would make a fine non-combat ESC, just not tough enough for our sport .

had one of these back in the day, pretty bulletproof to be honest with u, had mine running 4 300 watt motors at 36 volts with the 8:1 reduction oatley sells and moving a platform weighing damn near 100 kg and it performed flawlessly.

Only issue is its end of line item and if something breaks you cannot get it fixed easily and i dont remember anyone selling them still.

ha ha, if u can hunt down jeff ferrara, i think he has two broken ones sitting round he may part with
_________________
Andrew Welch, Team Unconventional Robotics

the sabertooth 2x50 might be localy sourcable in the future migh be worth an email to that robotparts guy see if he plans on importing.

If an xxl is too low speced then a 2x25 does not stand a chance.

noticed the ibc is v2 on rmp so gets to avoid all the bad reviews of the v1.
_________________
Remember to trust me, I am an Engineer.

http://www.youtube.com/watch?v=rp8hvyjZWHs

Thats good to hear - There was an reason (unfortunately beyond Jason's Control - one of his suppliers let him down) to do with the recent increase in complaints about the IBC that was seen on RMP, that has now been fixed. It only affected the last batch and was part of the motivation for the circuit board revision, so it should be back to normal now.
If anyone wants to known more, ask "out the back" and I'll tell you the details.
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people

Moving on from ESC choices, what are people's feelings about battery choices for a newbie bot? We all know the characteristics of the various battery chemistries; is NiMH dumbing it down too far nowadays? Is Lipo still too dangerous and are A123 cells reliable enough?

Looking at the RMP, Nicad and NIMH packs don't have any price advantage over A123 packs of similar voltage and AH ratings for this particular project. A 4 cell, 13.2V A123 pack is $69 for a generic pack and $89 for an 'official' A123 Racing pack.

The closest NiNH pack is $96 for a 14.4V, 4.6AH model, which is a bit overrated for this project IMHO. A 14.4V, 3AH Nicad pack is $90 and is almost 4 times heavier than the A123 pack.

Without thinking about it too much, my preference its to go with commercial A123 packs for the basic bot and Lipo or Lithium Manganese packs with balance connectors for the premium bot.

Would anyone happen to know how wide an A123 pack in a 'Vee brick' formation is?

putting a keyway on our wheels doesn't look that hard.
If there is some interest we will add that to the product line.
_________________
Mechanical engineers build weapons, civil engineers build targets

You are always welcome to use my 3 ton press to broach hubs.

A123s are the way to go. I'll go measure a staggered brick pack today.
_________________
( •_•)

( •_•)>⌐■-■

(⌐■_■)

YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH