First Robot

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longhairedsi
Posts: 2
Joined: Wed Sep 11, 2013 8:19 pm
Location: Hurstpierpoint, Sussex

First Robot

Post by longhairedsi »

Hi Friends,

I'm about to attempt to build my first ant weight robot with my 7 year old and have no previous robot or electronics experience. I've been reading this awesome tutorial and think I understand most of what needs to be done:
http://homepage.ntlworld.com/g0xan/robo ... iagram.htm

Using the links/codes in the tutorial come up with the list of components below, do this look OK?. The only thing I'm not clear on is the speed controller, in the tutorial it mentions using re-purposing a 'servo controller board' I'm not 100% sure go to go about this and what to buy, could someone help me out? :)

Transmitter
Planet T5 -£51.99
http://www.coolcomponents.co.uk/catalog ... p-910.html

motors
pololu 50:1 Micro Metal Gearmotor HP - £13.00
http://www.hobbytronics.co.uk/mm-gear-m ... =MMGEARMOT

wheels
Pololu Wheel 32x7mm Pair - Black - £5.50
http://www.hobbytronics.co.uk/wheel-32-7?keyword=1087

Pololu Wheel 42x19mm Pair - £5.50
http://www.hobbytronics.co.uk/wheel-42- ... lu%20wheel

motor bracket
Pololu Micro Metal Gearmotor Bracket Extended Pair - £3.79
http://www.hobbytronics.co.uk/motor-con ... racket-ext

weapon servo
Sparkfun Medium Servo - £8.95
http://www.hobbytronics.co.uk/medium-se ... ol%20servo

Voltage regulator
7805 5V 1A Voltage Regulator - £0.40
http://www.hobbytronics.co.uk/voltage-r ... ord=MC7805

switch
Switch Harness with BEC Connector- £4.31
http://www.technobotsonline.com/switch- ... ector.html

battery
HYPERION G3 CX-25C 0320-2S LIPO - £6.92
http://robotbirds.com/catalog/product_i ... ts_id=5743

charger
GT Power B606 balance Charger Li-po NI-MH Battery -£20.50
http://www.giantshark.co.uk/product/170 ... mh-battery

Thanks!
Simon
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Rhys
Posts: 738
Joined: Tue Oct 29, 2002 12:00 am
Location: Caerphilly, South Wales

Re: First Robot

Post by Rhys »

Hi Simon,

That's a pretty solid looking list of components. The charger looks like a rebadged Accucel 6, which I've used for antweights and featherweights, and is more than up to the job. You will also need a DC power supply to power it. The motors, transmitter and wheels/brackets have all been used before to good effect. The only unknown quantity would be the servo, I've never seen anybody use one of these. But Sparkfun have a pretty good reputation, so I wouldn't worry about that. What do you need a 180 degree servo for? Or is it top secret? :P

The battery is a fair bit bigger than you would really need for competition. But if you can spare the weight, then that's fine. The one you've linked to is 320mah. I generally use 120mah for a fliper/pusher, and 180mah for a spinner. It's only a saving of about 6-10g, but every bit counts!

As for the speed control, if you want to 're-purpose a servo control board', then get the biggest, cheapest servo you can. Usually you can get a 50g servo for about a fiver. You will need one for each motor. Something like this would be ideal. Take it apart and you will see a small motor. Solder this out of the servo control board, and then solder your pololu motor in its place. Sadly though, I don't think servo boards will handle a HP motor, you may have to go with the standard pololu motors. Or get a proper speed controller.
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BeligerAnt
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Location: Brighton
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Re: First Robot

Post by BeligerAnt »

Hi Simon, welcome to the forum.

One thing you might need to consider with the Planet T5 is the issue of mixing. Antweights use "tank style" steering and to give a normal response to a joystick they require the 2 joystick channels to be "mixed". Basically one wheel responds to the sum of the forward/reverse and left/right channels, the other motor responds to the difference.

The Planet T5 doesn't include mixing so you would need to add a mixer into the robot. Alternatively you could look for a transmitter with mixing built in - it saves a little weight in the robot! You need "elevon" or "delta wing" mixing - consider the Spektrum DX4e. Alternatively an on-board mixer is not very expensive.

If you go for the DX4e you will need to buy a separate receiver. There are several "DSM2 compatible" receivers which have been used in many ants, you don't need to splash out for a genuine Spektrum one.

One day I will get round to writing a step-by-step guide to making a speed controller out of a servo board but it's unlikely to be very soon. I haven't had a problem with using servo boards with the HP motors, but others have reported that they don't last too long.

Good luck with the build, keep us posted!
Gary, Team BeligerAnt
danjr1
Posts: 26
Joined: Fri Sep 03, 2010 11:54 am

Re: First Robot

Post by danjr1 »

BeligerAnt wrote:One day I will get round to writing a step-by-step guide to making a speed controller out of a servo board but it's unlikely to be very soon. I haven't had a problem with using servo boards with the HP motors, but others have reported that they don't last too long.
Found this online a while back, is what im planning to use:

http://www.rcgroups.com/forums/showthread.php?t=1715896
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longhairedsi
Posts: 2
Joined: Wed Sep 11, 2013 8:19 pm
Location: Hurstpierpoint, Sussex

Re: First Robot

Post by longhairedsi »

Thanks guys, very helpful!

@duff
What do you need a 180 degree servo for? Or is it top secret?
Hahaha, i wish i had a secret plan :) but it's more of me not really knowing what to buy :).
As for the speed control, if you want to 're-purpose a servo control board', then get the biggest, cheapest servo you can. Usually you can get a 50g servo for about a fiver. You will need one for each motor. Something like this would be ideal. Take it apart and you will see a small motor. Solder this out of the servo control board, and then solder your pololu motor in its place. Sadly though, I don't think servo boards will handle a HP motor, you may have to go with the standard pololu motors. Or get a proper speed controller.
Nice info, i didn't know what HP meant, guessing now it's High Power or such like? I'll have a look at proper speed controllers and smaller motors

@BeligerAnt
The Planet T5 doesn't include mixing so you would need to add a mixer into the robot. Alternatively you could look for a transmitter with mixing built in - it saves a little weight in the robot! You need "elevon" or "delta wing" mixing - consider the Spektrum DX4e. Alternatively an on-board mixer is not very expensive.
Nice info, i think I'm going to switch to a Spektrum, I'm trying to keep the build as simple as possible for now.

@danjr1
Found this online a while back, is what im planning to use:

http://www.rcgroups.com/forums/showthread.php?t=1715896
Nice! :)
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