4QD NCC 70 OR PRO 120

Hi which speed controller is better for use with 24v Bosch 750w motors, which one is more reliable.
Cheers Danny

:)

what does the smiley face mean

http://www.extremefightingmachines.co.uk/cgi-bin/discus/show.cgi?tpc=9&post=23285#POST23285http://www.extremefightingmachines.c...pc=9&post=2328 5#POST23285

750W at 24V is only 31.25 Amps. If you have a big gear ratio then the 70s will be fine but your robot will be slow. On the other hand if you uses a small gear ratio then the motor will be doing more work during acceleration and will most likely need the extra amps. Both are very similair but we went for the 120s to be safe and they are supoposed to be more reliable as they are not stressed as much with the same motor.

Ive adjusted the Pro 120s currnt limit down to 70 Amps for drive anyway, purely to prolong battery life and to give better protection during stall.

Bosch 750s on NCC70s are fine - if installed properly. We have used ours on 24v and then modified the NCC70s for 36v (actually made them switchable) This is explained on the 4QD site and is quite easy. Our gearing was poor (10 dia wheels and only a 9 to 50 reduction from the motor) which meant sluggish acceleration, high top speed and a BIG current draw from stationary. The NCC70s were fine.
The main thing to think about is mechanical support and heatsinking. I strongly suggest that you mount the big ally heatsink onto another big chunk of ally, ideally part of your chassis - and use heatsink compound between the faces - and thread locker on the fastners! Then make stand-offs to suit the 4 corner mounting points. These must fit properly without stressing the board. Thread lock them too. Final word of advice, fit the boards as close as you can to the centre of your bot - the inertial loads set up in the board when your bot is bashed by a super flipper or FBS are minimised. The loads are much, much worse if you mount the boards at the ends or edges of your bot. A sensible installation and you will be fine with NCC70s. Avoid DC111 mixers though - these are awful and there are many better and cheaper around - Delbots etc.
For series 7, we took off the Bosches - to save weight, we went to Iskras for drive, leaving 2 Bosches on NCC70s for the disks.

Richard
13 Black

right thanx everyone, i have now decided to go with the ncc 70, however after reading this: If you inadvertently connect the battery up the wrong way round - the controller will be destroyed - in quite a spectacular manner! of the 4qd website i think i need some reverse polarity protection, any good ways anyone?
thanks.

From an untutored viewpoint...

Coloured cables? Honking great diode? Diode enabling the failsafe relay?

--
Fluppet

talking of cables, where does everyone get high current cable from

I got some 40A figure 8 (black and red) cable from maplin - something like £2/metre. I think they do one higher than that as well.

-- Kev

Got ours from Marionville Model shop in Scotland. High Cuurent, High Temperature, High flexable Silicon insulated wire. 4mm sqr Area with 512 conductors. Wire marking Ultimate wire from some American company.

Id Recommend 6mm wire for your battery leads and Yes colours are better. Dont think your saving money buying just one colour it gets confusing.

ive priced up in rapid electronics, red & black 6mm cable 27 odd pound a roll 100m, im gonna get these. 55A the rating, i thought i would need 70A cable.

Danny

why dont buying it on a gas-station ?

I managed to pick up a small reel of super-dupa thick earthing cable from a local DIY stores closure sale for a £5! Copes with high currents fine, only problem being its all yellow&green so all wires need labelling.