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Nick
Experienced Roboteer
Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW
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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.
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Mon Dec 28, 2009 10:28 pm |
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Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
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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
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Mon Dec 28, 2009 11:26 pm |
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