Team MedBots

[Max]

Hey Guys,
2 related questions:
-Can the servo boards from SG90s run the normal micro gearmotors on 2s?
-alternatively could the BEC in a brushless esc supply enough power to drive 2 SG90s running gearmotors?
Trying to come up with a list of components for the cheapest possible competitive Antweight

[Rapidrory]

Cheapest possible would probably be to use full rotation hacked SG90s with a Lemon RX and a 6v Nimh battery or a 1S lipo; some people still use them, although making them competitive is tricky (antroboteer is the expert on low cost robots :L). That would come to about £9 for the whole drive setup assuming a 1S lipo and not including postage.

SG90 boards will drive the £2 chinese gear motors most people use these days, but any more than 6v and they start to get very jittery (I've tried it). Should be able to run it off a brushless BEC fine though assuming you want to still run 2S.

Alternatively you could have another crack at making your own ESCs; each of my boards cost me about the same as 2 SG90s to make. This is why I developed them in the first place :L

[AntRoboteer]

antroboteer is the expert on low cost robots :L

Why thank you very much!

We've found you can use SG90 servo boards can work with a nice LiPo as long as it's regulated down to 6V. I'm not at all sure about BECs but we use 7806CV regulators on the output of a 2S for this and so far they have worked admirably despite running rather warm under high load.

Just remove the potentiometer and create an adequate potential divider using some resistors and you should be good to go for driving a couple of gear motors if required. We use combinations of 2.2K resistors in parallel to make up a certain ratio of resistance either side of the middle terminal which we have found varies between different seemingly identical boards.

If you don't want to start making your own regulated battery switches in order run these servos or just the boards for gear motors then I would recommend the 5 cell NiMH packs from the component shop.

Link: http://www.componentshop.co.uk/6v-1-4aa ... -pack.html

They've been very good for us so far except when you use them for an immensely powerful servo such as a Park HPX F at the same time as your drive which draws too much current. That brings back really awful memories of my best flipper robot, Hoondal, flailing about and just losing control altogether. It had such a good flip; pity nobody ever got far enough onto the flipper for it to do anything except break down when I tried to self right.

I agree with Rory's suggestion of a Lemon RX; just switched over a couple of robots from OrangeRXs and they are so much better in every respect as well as cheaper. Definitely get a LemonRX!

If you do choose to go with 360 modded SG90s, make sure you have large enough wheels such that the robot runs at a decent speed. I would suggest no smaller 5cm in diameter to ensure the robot is fast enough. I've had enough success with hacked SG90s to recommend them for people wanting the most inexpensive and most robust drive setup possible but I think you'll find you may want to just use the boards for gear motors further down the line.

[Max]

Hey,
I'm going to try out the SG90s running regular gearmotors, has anyone got a pair of gearmotors they'd be happy to sell? I need some asap to make up a prototype to check/show all the planned components work together before my Uni robotics club orders a bunch.

[Hogi]

i think Will sells them on his website. shockbots.co.uk

[Max]

Can't see them there...

[Occashokka]

Although he's very busy Rory probably has a stock of them from China that aren't going to be too expensive

[Shakey]

I sell them if you need some though I'm pretty busy with uni stuff so not sure if I can post quickly.

[Max]

Anyone got some they could send on Monday/Tuesday?

[AntRoboteer]

These are perfect if you need them in a hurry:

http://www.hobbyking.co.uk/hobbyking/st ... duct=89146