Feather weight speed controllers

Im planning to make a feather weight robot, but first im making a kind of prototype robot which runs on two 9.6 volt drill motors, hooked up to one 9.6 volt battery but the problem is i dont know which speed controllers to get.

at a model shop called geedee model shop in nottingham near me, they are selling marine speed controllers running at for example 15A which say.....

The Viper 15 is a reversible marine spec speed controller capable of handling upto 12v 15A max.
NEW built in failsafe to protect against complete loss of signal or when out of range.

would 2 of these do the job? they cost £21 for 1

Any ideas?

If you would try it, I suggest fitting fuses of 15A to the main leads. if these blow a few times in non combat, forget these speedos.

Also, its better to invest in the right stuff from the start, otherwise you end up, like me, with a pile of parts that arent really usable and still sucked my wallet dry.

The other thing is that buying 12V speedos now will limit your upgrade possiblities. It would be better to get some 24V speedos like electronize (availiable from technobots.co.uk). And use them on 12V as 9.6V drills should be able to handle 12V.

As Ed said ...spend a few pounds more and get a speed controller that is commonly used in the Robot community and gives a wide voltage spread.

Ed mentioned the Electronize ...Technobots do a range of controllers e.g.

Sabertooth Dual 25A Motor Controller Universal.

http://www.technobots.co.uk/acatalog/Online_Catalogue_Dimension_Engineering_Controllers _34.htmlhttp://www.technobots.co.uk/acatalog...gineering_Cont rollers_34.html


Double the price of your two Viper Mtroniks Escs
http://www.mtroniks.net/mtroniks_SC_products.asp?CategoryID=1&SubCategoryI D=3http://www.mtroniks.net/mtroniks_SC_...ubCategoryID=3
.... but probably worth it in the long term.

http://www.dimensionengineering.com/http://www.dimensionengineering.com/ same but cheeper price in USD, USD is VEERY low right now, try Sabertooth dual 10A motor driver for R/C - 65 USD - OR Sabertooth dual 25A motor driver - 125 USD -

The Robot Power Scorpion XXL is another possibility ... Ive recently purchased but not yet received this controller.
http://www.robotpower.com/catalog/http://www.robotpower.com/catalog/

Note that it only shipped two days ago ...so no gripes on time....yet:).

(Message edited by woody on April 19, 2008)

Mats, $65 = £34, add to this 4% import duty and then VAT you get £41.55 which is greater than Technobots £38.95 for the 2x10A RC, so how is it cheaper?

thnx very much thats all very helpful, its looking like for now due to the amount of money i have etc ill get the Sabertooth Dual 10A Motor Controller for RC which is £40

But im not 100% sure about something because ive not been doing this kind of thing very long,
but the motors are too fast and need slowing down, can I adjust the settings on the speed controller, or does it work on the more i would push the stick forward the more voltage is supplied to the motors- thus making them go faster?

The speed varies in relation to the stick position .... OFF at centre and a progressive increase as you move the stick foward / reverse ....& left / right if using just one Transmitter stick and mixing the R/C channels.



http://www.4qd.co.uk/robot/start.htmlhttp://www.4qd.co.uk/robot/start.html

(Message edited by woody on April 20, 2008)

There are 3 ways of solving this:

1: get more reduction behind the motor so the wheels turn slower if the motor is running full power (that is the best way, you will have more power and your speed controller(s) have to work less) but unfortunately that is not always possible.

2: reduce the amount of stick travel, make a small plate that fits over the stick with a circle that is less large than the maximum stick. Ive seen some people do that with transmitters that dont have option 3.

3: If you have a transmitter that can do it, change the settings on your transmitter that stick travel is only a certain percentage. With Dual rate you could flick a switch and then have your sticks at a lower percentage if you push it all the way out. I do that with Hannibalito 3, it drives normally at 45% of its top speed unless I flick the switch.

im making a kind of prototype robot which runs on two 9.6 volt drill motors and gearboxes?
Simply replacing the drill chuck with a wheel of between 80mm - 100mm dia is standard practice in bot building.

Good decision not to go with the Viper M tronics for a feather. I once did a 6 kg feather with them, runing 2 x 9.6 volt drill motors. They worked but they were not quite enough and sometimes went into thermal cutout. I retired them to a 1.3 kg robot driven by electric screwdrivers and they have been performing well ever since.

Has anyone ever tested the Sabertooth controllers with a data logger to find out if they perform to their reported amperage in the arena?

Sabretooths in my experience are far short of their 25Amps rated. They have blown twice on me so I have given up and gone back to 15amp electronize. Only blew on of them for the first time this weekend and even then its only the relay which will take a half hour to replace.

Philip, I have and they unlike another well known brand I could mention do perform to their published spec and that is also guranteed by Dimension Engineering. I have run a pair of 15A electronize controllers with eight 30W motors in parallel and never blown a relay. As I have mentioned before Gary, its all about knowing what your motors take under all conditions especially stall current which is what is the controller will see when suddenly reversing direction.

Thank you. It is good to be able to hear of others experience.

No problem Paul. I was just passing on my experience with the controllers. They handled beautifully when they worked in hornet.

Only blew one of them for the first time this weekend and even then its only the relay which will take a half hour to replace.

As Paul has said in the other thread ...Gary, there is has to something a miss with your set up that is causing the problem with the Sabretooth but no idea what

Was it the same drive side blown each time the controller failed?...if so Id suggest you replace the drive & motor that the burnt Electronize relay was supplying.

I run 2 Graupner speed 900s on 13.1V and 24V on the Scorpion XXL without any problems whatsoever, no matter what pushing match i was in with any feather of ours.

It is all about matching motors & gearing to the controller.
Leo appears to have got it right.

My XXL however isnt a match for my present motors and current limits constantly.

Investigation of my drill motors via the web ( based purely on can dimensions and voltage ) suggest that they may well have a stall current exceeding 100 amps@ 18v ....Im running 24v.

http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=rs_775vcwchttp://www.mabuchi-motor.co.jp/cgi-b..._ID=rs_775vcwc

Time to change motors me thinks....

(Message edited by woody on May 26, 2008)

No problem Gary and as you stated in your experience. Current limiting when implemented in software has an execute time that can be slower than peak rush current. I wonder if your reversing currents exceed the peak rating of the MOSFETs and they pop. In the Electronize, excessive reversing current takes out the relay first. Or as Woody suggests, maybe a motor on its way out.

Woody, 100A stall - ouch! One reason why I shy away from recommending specific speed controllers for drill motors as their full performance is rarely known.

Speed 900s give 65A stall current @12V. We measured about 20A onder load on a 9:2 gear ratio and 70mm wheels in both Hannibalitos.

We do use active cooling on ours though. The scorpions are in a box with 2 small fans, 1 blowing in the box from one side and 1 drawing the air out from the other.

We also ran 4 speed 900s on 24V on 2 XXLs with a 6:1 ratio and 100mm wheels, where we drew so much the battery packs started melting but the XXLs never blinked once. We never stalled that one though.

Sabertooth or Scorpian XXL?

The numbers say Sabertooth but what is everyones view in practice?

Which one is performs better?

Personally, I dont think there is much difference between them. I will say that I dont like the way Robotpower makes the XXL, but we do our own version of upgrade that is a lot better.

(Message edited by leorcc on June 03, 2008)