Total Newbie on a budget

I'm completely new to this and although I've looked around I can't really find any good general build guides. They all seem to suggest parts that I either can't get or are expensive.

For my first robot I want to build a seriously cheap setup spending as little as possible. With a view to upgrading later if I enjoy the experience of building one, rather than spending a lot and having a big robot in the shed doing nothing that cost too much.

Would the following parts work? If not can you suggest better for a similar price?

Transmitter: Flysky FS-CT6B (With receiver that comes with it)
http://www.ebay.co.uk/itm/291967137796

Motors: 2 cordless battery drill motors.

Speed controllers: (x2) http://www.ebay.co.uk/itm/401090473474

Battery:
http://www.ebay.co.uk/itm/391650060380

I think everything else is easy enough to source from what I have lying around like the wheels and chassis etc. I would just like to know if those items above would work together.

That ESC won't work with batterydrills.
It's a brushless ESC, ment for completely different motors. Also, even if you would change the motors to brushless motors, that ESC can mak'em turn in 1 direction, not reversing.

Also, ESC's ain't something you should be skimping on. It is rarely a good ESC will fail you.
The Ranglebox/BotBitz 30A or the way stronger TZ85a's are the primary choise in the UK.
There are dedicated Featherweight 2 channel ESC's
Robot Power Scorpions is a known quantity, but expensive .
The German IBF 4.5 is quite a bit cheaper, and is rock solid. Even if the amp rating looks a tad low.

The battery, too expensive for what you want/need. This delivers more volt (11.1 compared to 7.4) for a way cheaper price

Thanks for your reply.

I saw those botbitz ESC's mentioned a lot but both are out of stock. I can't find the IBF 4.5 for sale in the UK, I'll keep looking.

Thanks for the link to the battery, I'll order one once I've sorted the esc.

Do you know anything about the flysky transmitter?

The IBF can only be bought from the maker, Reinhard. You even can ask for custom work.

On FlySky, good stuff. We use'm to.

Are there any esc''s like the 85a I can get to play around with until they are available again? Something from eBay or whatever that won't break the bank and can be chucked once I get the proper one? Just to get started and the thing moving etc.

Hobbyking sells the TZ85a's , but programmed for Brushless motor control.

The code needed to reprogram those is freeware. Some people on the forum can reprogram those ESC's.
But I'm not one of them, and bought TZ85's from Botbitz and Ranglebox in the past.

Didn't want to start a new thread for a basic question like this so thought I'd ask here.

How hot do the electrics get on a featherweight using a 3s battery, 2 drill motors and 2 30a escs? Is it enough to be concerned about or can I stuff all the cables etc together into a small space between the motors? Or should the wires be spaced out around the chassis as much as possible?

Heat becomes a problem when you start overvolting motors.
But 12V motors on 3S, that's rather safe in that respect.

Don't worry. Just keep wiring and such neat.

A big bowl of electrical wire spaghetti in the robot just takes space, weight and annoys to no end.

I've run drill motors on 30a botbitz and 6s before now and they've been fine, so you've no need to worry in that regard. Can't recommend 6s too highly though lol

Thanks. I've put all the wires etc into a little box beween the motors to neaten it up and protect them a bit.

You said you use the flysky. I have the CT6B and I'm wondering how have you set yours for steering? I can't work out how to make it steer with both wheel's.

Ive got it so when I push the right stick forward and back both wheels go together.
Then I've set the left stick to steer but can only get it to operate one wheel. What I want to do is turn the left stick left and both wheels rotate opposite directions to turn and the other way when I go right.

Is that possible with the flysky?

Quote:

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Originally Posted by Flag Captured

I've run drill motors on 30a botbitz and 6s before now and they've been fine, so you've no need to worry in that regard. Can't recommend 6s too highly though lol

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Why no love for 6s?

Quote:

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Originally Posted by Londonboii

Thanks. I've put all the wires etc into a little box beween the motors to neaten it up and protect them a bit.

You said you use the flysky. I have the CT6B and I'm wondering how have you set yours for steering? I can't work out how to make it steer with both wheel's.

Ive got it so when I push the right stick forward and back both wheels go together.
Then I've set the left stick to steer but can only get it to operate one wheel. What I want to do is turn the left stick left and both wheels rotate opposite directions to turn and the other way when I go right.

Is that possible with the flysky?

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And yeah that should be possible. I don't own that transmitter but the setup you want is a pretty standard mixing setting.

If, for whatever reason, the transmitter won't do what you want, you can install a plug and play mixer between the ESCs and receiver in your robot and leave the transmitter unmixed for the same result.


Hope it works out

I got a separate mtronics tank mixer for about a tenner - tiny little unit that just plugs between the receiver and speed controllers. Only had it running with test gear so far but it seems to work great.

Thanks. At the moment I have it setup like so.

Motors/ESCs connected to CH1 and CH2 (right stick)

CH1 (up down on right stick) is mixed to CH2 so up down controls both wheels forward and back.

CH2 (left right on right stick) controls one wheel but I won't use it.

CH3 (left right on left stick) is mixed to CH1, so when I turn left the left wheel goes back, when I turn right it goes forward.

How would I use the plug and play mixer in amongst that setup to get CH3 control both wheels, turning in opposite directions?

Quote:

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Originally Posted by Londonboii

How would I use the plug and play mixer in amongst that setup to get CH3 control both wheels, turning in opposite directions?

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I haven't tested if it reverses one side in a turn. The point of little units like the mtronic is that there aren't any settings to worry about so I would imagine it either works or it doesn't.

Might have everything running properly at the weekend, so will check then.

A plug and play mixer would require no mixing on your transmitter, with channels 1 and 3 on the transmitters directly controlling the 2 used channels on the receiver.

I know it might be cheating but could you get hold of a ready to use V-tail mixing model for your tx? That would get you there straight away.

From the sound of it the physical mixer is just going to do what the program does.

I need to get ch3 left to control ch1 forward and ch2 in reverse, and ch3 right to control ch1 in reverse and ch2 forward.

So I think I'm trying to split channel 3 into 2 channels, with each one controlling the 2 in different directions. If that makes sense.

Maybe it would be easier to have each stick control a wheel and then I could turn by having one up and one down. But the left stick doesn't return to centre when released like the right. It sits where you leave it and it's not easy to centre without looking.

I'll look at what the v tail mixer does.

Quote:

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I know it might be cheating but could you get hold of a ready to use V-tail mixing model for your tx? That would get you there straight away.

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That wasn't very clear of me. I meant - there must be a default tx programming file available somewhere with V-tail mixing taken care of. I'm not an expert in the slightest in programming that tx but I thought it might be a shortcut worth tracking down :)

Getting a physical mixer might be a bit silly as you say.

After looking a bit it looks like it's possible to mod the left stick to make it sprung, which will mean I can just operate each wheel sperately and I'll then just move them in opposite directions to turn.

Thanks for the help

I got the controls sorted by modding the left stick so it's sprung now.

Further questions:

I'm using 2 cordless drill motors and holding the wheels on with the reverse thread screws. They keep working loose. Anyone know how to prevent this or if there are stronger reverse thread bolts to hold them on with? The screw isn't made of the strongest metal and I've almost ruined one of the Philips heads.

Also looking forward to the weapon, I'm going to use a linear actuator to raise the lifting mechanism.

What do I need to connect the linear actuator to the receiver and control it? Something like what the escs do on the motors. Would a simple on/off do the job? Or is there something better for this?

I'll be using a switch on the transmitter to activate the lifter.

If you're keeping it simple and using a single switch for the weapon then a set of RC switch + relays would do fine (plus some microswitches for end stops if the LinAc doesn't have a limit switch of its own) to just flip it between the battery voltage in either direction. You'd have to do some simple circuit design to get the receiver signal controlling it properly.

Alternatively, you could get a reversible brushed ESC but if your not worried about controlling the speed then you'd be wasting some functionality.

Thanks.

If I use a mondeo seat height adjusting motor with the threaded rod arm as in the car would a brushed ESC similar to what I use on the motors for the wheels be all I need?

I think it has end stops when in the car as they stop at certain heights. But I'll look at that when I get it.

If what you salvage from the mondeo has some sort of end stop switches then possibly (assuming it's a suitable motor :P)

Bare in mind you don't just need physical end stops that stop the motor turning, they need to actively cut off power supply to the motor in their respective directions when the limits of the lin-ac are reached. The controller won't know when to stop on its own and will stall the motor at the limits of movement, which you don't want.

Lots of off the shelf lin-acs have this built in so you can drive them against their limits of movement and they won't stall, a bit like this:
https://s3-eu-west-1.amazonaws.com/g...tch-layout.jpg

I'm not too good with electric drawings, and haven't done much with relays.

But is that a drawing of 2 relays connected to the motor? So there would be a physical connection made at each end that tells the relays to cut off power to the motor once it's reached each end of travel?

Are they just standard auto 12v relays? Each point on the NC parts are the 4 pins on the relays?

They're just two microswitches, and each has a diode connected to it. This allows power to travel in one direction only. The idea being that when something reaches the end of its travel, it hits the switch which cuts the power to it, thus protecting the mechanical bits. But it only cuts power in one direction, allowing you to reverse/retract the motor to reset or reposition it. A microswitch at the other end of the travel will cut power there too. I fitted these on my featherweight grabber bot and they worked pretty well.

https://youtu.be/2TZ1lS8I-lg

That diagram shows the typical set up for using switches at the ends of travel to stop current flowing and letting the motor push it any further, sorry for being confusing :P

The ends with V+/- are the voltage you would be supplying from your ESC. The things labeled "NC" represent switches that are activated when the limit is reached, one for each end; NC stands for normally closed, so when it hits the end, they are opened.

The components represented by the arrow and line are diodes. Their function is to only let current flow in one direction.

The M in the circle is the motor driving the lin-ac.

Imagine the lifter is halfway up. Both switches are closed, so the diodes are redundant/bypassed and current can flow in either direction i.e. you can tell the ESC/relays to provide a voltage across the circuit in either direction and the motor can spin in either direction, raising it up or down.

Now the lifter hits the top of it's path, you don't want the motor to try and keep pushing because you'll break the mechanism or stall the motor. One of the switches is at the extreme however and is activated/opens. This means that if current wants to flow through the circuit it has to bypass the switch and flow through the diode instead of the switch. The diode won't let current flow in the direction that would result in the motor trying to push the lifter beyond its limit.

The other switch is still closed so it can still move back.

The same thing happens with the second switch and diode for the other limit.

Hope that's more helpful.

EDIT: Ah, got beaten to it :P

Thanks a lot both of you. I think I understand now.

Last silly question, what diode do I need?

I searched in maplin for the micro switches and they are simple enough, but search diode and a load of different types come up.

Is there a name for the type of diode in that setup?

Will this work? Using 3 pin microswitches.

If the diodes are needed, where would they go in this setup?

Attachment 6406

You do need diodes here, because otherwise, your linac will disconnect permanently when it gets to one end. Think of it this way: The diagram Bitternboy posted shows a circuit where there are two one-way paths for the current to follow, and a path for current to flow in either direction (if both switches are closed). Now if one switch opens (or disconnects), the current can only flow one way through the circuit now because the current is now forced across the diode that is connected over the switch. This means that, while the circuitry will stop your motor from trying to push the linac past its limits, it will still allow current to flow in the opposite direction so you can retract it.

Your diagram would stop the linac moving completely since it pulls both contacts of the motor to the same voltage, which then stops it (I think). You basically just need to make something like Bitternboy posted. The diodes you need can be fairly basic, you just need ones with a higher reverse voltage than you're running your motor at, and some that can handle the current through it (which you can measure while it's running). Also keep in mind that diodes introduce a small voltage drop when used (usually around 0.7-1V) but as long as your linac can move off the limit switch again, it'll be fine.
Something like this should do, but check your voltage and current as I said: https://www.arrow.com/en/products/1n...FQMM0wodY6MGTA

Oh, and don't get Zener diodes. They're not what you need here.

So like this?

Attachment 6408

Using simple limit switches like these and diodes like the ones you showed (depending on voltage etc)

http://www.maplin.co.uk/p/low-cost-s...FYU_Gwods_8OEA

Yeah that's fine, assuming you're using a forward/reverse RC switch for your ON/OFF block there, rather than a speed controller. If you were using a speed controller, you wouldn't put your battery in series with the rest of the stuff, it'd be the controller instead.

I was going to use an receiver controlled on off. But if a reversible rc switch works I will do that

Well either way, you need the receiver. But just turning the motor on or off will only allow you to move the linac one way. Remember you need a means of causing the current to flow over the motor in the opposite direction in order to retract the thing, either by switching the polarity or with an ESC.

Apologies for the length of this and the amount of questions. I have now built a very basic robot, after lots of reading and messing about I have something that drives and has a pneumatic lifter. I was going to use a linear actuator but just couldn't get the lifter fast enough. I have learnt a lot from various threads here but some posts get a bit technical and some answers seem to contradict each other. I assume that's due to some rules changing over the years or different ways people interpret compliance.

My questions are regarding making sure my final design meets the safety requirements of the rules, now I know I can get it working.

Electrical
1 - I have a removable link (a fuse in a holder) how do people make it accessible from the outside? Just a flap on the shell? How is this kept closed so it doesn't come off in battle but is still easily removed when needed?

2 - how do you test that the receiver failsafe works? There's a light on my receiver. Turn on the transmitter and it's on. Turn off the transmitter and it's off. That shows the failsafe is working, right?

Pneumatic
The rules aren't very clear on what's needed here. To me at least.

3 - I'm using a paintball Co2 tank so assume the burst disk on it is all that's needed between it and the regulator to comply with the pressure release rules?
4 - the regulator drop's the pressure so that it's below the 10 bar limit of my ram. So in this section I need a 10 bar PRV that'll open and release the pressure if it goes above 10 bar for some reason? Can this be anywhere between the regulator and the ram?
5 - I believe I need to add a QEV to dump all the gas in an emergency. Is that correct? This also needs to be accessible from the outside? How do people achieve this? (similar to Q1 regarding the access flap/panel)
6 - I need an on/off so that there's no pressure in the system until it's in the arena about to battle? Can this just be a simple on/off valve after the regulator accessible from the outside as the QEV/removable link?

1) Open hole, a flap with a wing nut holding it closed, a flap on a slider. Many ways.
2) Drive full speed forwards and turn the transmitter off. Does it reset to 0?, does the weapons produce the same result?
3) Youll need a seperate PRV, rated to 1000 psi for full pressure or below your lowest components.
4) Yes, provided theres no one way section between components.
5) Same as 1, just get a ball valve of some sort or similar.
6) Unless an EO says - No, the On/Off needs to be directly after the bottle via either the paintball pin valve or via the bottle itself.

Thanks.

2 - I will check, but I'm pretty sure when I turn it off rolling it just rolls to a stop, there's no power to the motors. The weapon is activated fast, I couldn't check it in the same way but I suppose it's not needed if the other test shows the failsafe is OK? As both systems get their signal from the same receiver?
3 - so between the tank and regulator, I need a prv rated to 1000psi?
4 - I am using a 5/2 solenoid. So 1 prv between the regulator and solenoid would cover the lower pressure section I think?

Youll need to check drive and weapons independently.

During Tech Check it will be done without gas, but your valves will be tested via audio. You can however at the start plug a motor into each channel independently and test all channels using a single motor.

If the regulator fits directly onto the CO2 supply, then no. However youll need to double check with an EO depending on how your system works.

Yes, only advice ill give is to get the self reseting type.