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Last updated: 30 December 2001 Click Here to go back to the Power Controllers page
How do I properly size a speed controller to my motor?
You must know the stall current of your motor before you can size any ESC for your application. Techniques for determining this include manufacturer specifications and empirical measurements. Note that "free running current" is NOT the same as stall torque. The latter can be 4-5 times as high as the former!

How do I measure the stall current of my motor?
Buy a current shunt. Look in eBay. Shunts are nothing more than calibrated resistance elements. You wire them inline with your motor, attach your voltmeter to the shunt, lock the shaft of your motor and power it up while reading your voltmeter. Most shunts read a millivolt per amp which means that for every amp flowing through the shunt, the voltmeter reads 1mV. If you see 85mV on the display, 85 amps are flowing through the shunt. The ratio of mV/A is typically stamped onto the side of the shunt.

I didn't get any of that. Can I just pay you to measure my motor?

My motor pulls 75 amps at stall. Will the Victor 883 work for me?
It will work beautifully.

My motor pulls 175 amps at stall. Will the Victor 883 work for me?
It is unlikely.

Wait a minute - you list the Victor as one of the choices to run the Bosch GPA750! What's the deal?
Alexander Rose used this combo on the superheavyweight Toro at BattleBots without any problems. He overcame the high stall current of the Bosch by gearing it very low. This kept the Victor from melting. Obviously there was a lot of engineering in place here way beyond the simple "go, no-go" rules we all like to see. If you can match him, the Victor will run your Bosch motor.

I didn't take your advice above and it blew up. Can I fix it?
Unlikely. The driver chips are surface mount devices to reduce space and the electronics are "potted" to keep conductive crud out. You'll be fighting an uphill battle so best to spend the effort working overtime at your job to buy a replacement.

Can you or IFI repair it under warranty?
No, not if you exceeded the design current. If you are POSITIVE you did not and it is still busted, contact IFI directly for further instructions.

How high can I push the 24v limit?
There is some safety margin to account for residual battery charge (when fresh off the battery charger) but you should only run the 24v Victor on two 12v gell cells or twenty 1.2v nicad cells maximum.

Legend has it that you must cut the red wire between the Victor and the radio receiver. True?
Nope. It's a no-connect on the Victor PCB. The signal input to the Victor is optoisolated so as to not transmit ground noise back to the receiver. The only two wires that really count are white (signal) and black (signal ground.)

I hooked everything up properly and the the status LED just blinks. But when I plug an R/C servo into the same receiver channel it works fine. Is my Victor defective?
No you just need an inline signal buffer. Many radio receivers cannot source enough current on the R/C signal line to drive the Victor so an extra part is needed. Experience has shown that most Futaba receivers require the buffer, Hitec do not. The inline buffer is available from me, from IFI, and possibly from your local hobby shop. Alternate names are "elevon amplifier" and "long cable filter." We also sell them, above.

How do I get a "tank drive" setup going on one transmitter stick with these?
There are two ways. First you can just enable "elevon" mixing in your transmitter if supported. Second, you can buy one of my inline mixers (RCE540) and install it between your Rx and the Victors. Note that if you go with the inline mixer you do not need any inline amplifiers as the mixer also takes care of this. So that saves you some money!

Should I use the jumper in "brake" or "coast" mode?
Brake gives sharper response at the expense of greater wear-and-tear on your driveline mechanics. Coast is softer at the expense of control response. Experiment and see which works best for your robot.

Can I replace the supplied fan with a larger one and get higher current switching?
No, it has been aerodynamically tuned for the supplied geometry as well as the PC board traces. Don't mess with it.

Can I add heat sinks to the FETs get higher current switching?
No. Don't mess with them.

Can I run two Victors in parallel to control a higher power motor?
No way. Manufacturing variations between the two will eventually get them out of phase and they will fight each other. It's a game that has one winner and one loser.

But wait! I've heard of people running two Victors on a motor! What gives?
I too have heard of that configuration on motors that have a pair of isolated brushes. Apparently the scheme is to hook one Victor to each set of opposing brushes. Neither Team Delta nor IFI support this application, so play the game at your own risk!

Can I run two motors with one Victor?
Yes you can run two motors in parallel off a single Victor as long as both motors currents added together don't exceed the max rating of the Victor. Note that since each Victor provides ONE channel of control, and a tank-drive robot requires two channels, you will need two Victors at a minumum if you want to actually steer your robot.

Does mounting orientation matter?
Well if you're really pushing the current limit of the Victor, mount the fan upward so that if the FETs desolder themselves from the PCB at least they won't fall out!

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