Help with Building a Robot Power Distribution System

SRLM

I know, not a very concise title... If I think of something better, I'll change it.

Anyway, what I'm trying to do is to build a system to distribute battery power around my robot. The 'system' should have inputs of several batteries in parallel, and outputs to:
-Motor (~10 amps)
-Electronics (~1 amp)
-Servos (~3 amps)

Ideally, I'd like something that is clean insofar as that's it's a single board solution with neat wires, not a bunch of wires running all over the place to connect everything.

My problem is that I can't figure out a simple way to connect two large wires together that would qualify as clean. I'd like to use 10 gauge for the motor, and the batteries use 14 gauge. Somehow, without making a big mess, I need to connect it all together, preferably with solder. I don't have either the skills or tools to machine anything.

To complicate things slightly, I'd like to add a couple power switches for each of the components.

My potential solutions have been:
-Solder wires in a T shape to get multiple connections (difficult to cut the insulation in a band, soldering iron not powerful enough to solder the heavy wire).
-Create a bus with a flat metal stock, use crimp connectors to screw the wires to the bus (if I drop a screwdriver across the terminals there goes 40 or 50 amps...)
-Use terminal blocks (I'd still need to connect the blocks to some sort of wire, and I don't have the heat for that. Also, difficult to mount?)

Any suggestions?

mctrivia

don't solder then. twist wires together and use marets. if twisted correct there will be no problem.

or buy a jvc 50W iron

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

mctrivia

if you have exact design details I can build for you with terminal block attached

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

Ugha

Why not use some perf board and solder up the interconnects on that? Then just cover the back of the board in hot glue or electrical tape or something to insulate it, and bolt it onto your robot's
frame.
This'll let you put your switches whereever you want them.

Or use some molex connectors to connect to the perf board so everything is easily removable.

Another option for the switches are those in-line switches meant to go on lamps, you just hit the rocker switch and cut the + line going to whatever you want to cut off.

kwinn

To a great extent how you run the power is determined by how the circuitry is designed, distributed on the robot, and the number of separate supplies/batteries used.

It is a good idea to keep the motor supplies and wiring away from the control and sensor circuits, and also to separate the analog sensor circuits from the digital circuitry.

How many batteries and/or different power supplies are you using?

WBA Consulting

For the connections, I would recommend using standard insulated crimp terminals and 0.100" pitch DIP style PCB power taps. They should work with perfboard if that is your method.
search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=55556-4-ND

If you are making a PCB and can make use of larger holes, design in a standard PCB power tap such as:
search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=8190K-ND

I attached a picture of some of the DIP style ones used on a backplane for a 250W 5 volt power supply.

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Andrew Williams
WBA Consulting
IT / Web / PCB / Audio

Post Edited (WBA Consulting) : 4/14/2009 8:51:00 PM GMT

Desy2820

If the voltage is low enough, less than 30 volts or so, I'd look at car stereo accessories.· Probably overkill, but amp wiring kits would probably have some useful items.·

I'd consider using relays or solenoids·instead of direct wiring to switches.· This will allow you to run thinner, lighter guage wires with smaller switches, since you only have to worry about the coil current.

I hope this helps.

RobotWorkshop

You can use a combination of things to clean up the power wiring. Attached is a picture of what I used to distribute the power on the custom BOB project I had in SERVO last year. It uses a terminal block on the chassis where most of the power cables attach. There is also a fuse in each line where the power comes in from each battery. The whole system runs off 24V volts but some things tap off 12V from the first battery. From that 9V and 6V are done on a custom power board and there is a 5V 1amp DC/DC converter that handles all the logic. There were some painful parts in the project but it turned out better than I hoped and the robot is working well. Still have a few more sensors to add to it and then wrap up some more demos...

$WMc%

SRLM

I would invest in a good soldering iron. A Wellar 40 watter will fit most uses.
You would not believe the difference a good soldering iron makes.
A 40 watt Wellar will solder #12AWG wire all day long.!
They cost a little more, But are well worth their price.

I use a 20+ year old Wellar at least once a month at work.This Iron is shared between 4 other I/C Technicians.

___________$WMc%___________

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The Truth is out there············································ BoogerWoods, FL. USA

mctrivia

i would go with a 50W JBC more money but tips last for ever and they heat instantly and tips can be changed while hot unlike the wellars

I have the JBC AD2700. It has been discontinued in favor of the AD2950

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

Post Edited (mctrivia) : 4/15/2009 4:09:24 AM GMT

SRLM

Thanks for all the replies. I've got a guy nearby who has a PCB machine, and he said that he can cut one if I make the files. He also said that it's pretty easy to make something like this. I've never done any PCB work before, so I think this will be a good starting point.

I've got access to some nice Weller soldering stations like this, but I assumed that it wasn't hot enough. The consensus here is that 50W is hot enough, so I must be doing something wrong. How do I heat up a large wire like that? I put a ton of solder on the tip, and pressed the side about 1/8" from the end onto the wire bundle. Added some more solder. Nothing though.

I'll work on the design this weekend, and see if I can get a sketch out and posted.

mctrivia

jbc is hotter then weller because the heating element is in the tip not shaft but should still work.

what you need is a nice fat tip and heat up the copper trace and wire then press the solder against the joint on the other side until it melts together. remove heat but don't move wire until solder hard.

63/37 requires a lot less heat and has temp where it is plasticy.

lead free takes a lot of heat and there will be a point where it is not liquid and not hard. you will get a bad joint if the removes during that time

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

mctrivia

also be patient the more copper the longer it will take

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

kwinn

SLRM, you may want to buy an inexpensive soldering gun for the heavy duty work. I have an older Weller temperature controlled soldering station that I use for PCB work and a 100/150W soldering gun for use on the bigger stuff. This approach works very well.

mctrivia

be careful with guns they are fine to use on big stuff but make sure it is not near any ics the ones I have used where not esd safe

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

SRLM

Thanks for mentioning the solder gun. I'll look into it.

Okay, I've made up a sketch. I can only do single layer boards, so I'll need two jumpers to ground. The board is roughly life size with respect to the US quarter (about 2"x4"). The board has six heavy duty I/Os.

E: electronics, output only.
M: motor, output only. It will be routed through an HB-25.
B1, B2, B3: batteries, input to board, output to charge.
C: charger, input only to charge a single battery.


Then there are two 5V regulators to provide power to the servos. Those are in the boxes labeled '5V', with their pins on the inside. To the left of that is the servo output. It follows the standard -:+:S layout. Tied to the signal lines are inputs from the electronics board.

The board is designed with 7 switches: a switch for each of the main components: regulators (share a switch), electronics, motor, batteries, and charger. This brings up the main deficiency: the charger could be connected when multiple battery switches are on (when I only want to charge one battery at a time). I can't think of any way around this, so I'll just have to be careful.

I'll probably want to add some LEDs to indicate power, but that's about it.

Any comments? This will be my first PCB, so feedback is appreciated.

Post Edited (SRLM) : 4/25/2009 8:19:48 PM GMT

mctrivia

have you checked on a pcb trace calculator if the traces are big enough?

to what I can see looks good but I am on a cell

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Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.

kwinn

SLRM, I can see how this board will allow you to connect a charger to the "C" connection and select one battery to charge using the switches, but how do you get power from the batteries to the circuits they are driving?

As for your main deficiency you could use double throw switches (on, off, on) to connect for charging, running, or off.