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[on:]

I've currently joined a robotics group and the first glaring problem I found is we are using 4 different batteries in each robot as such:

12V battery -> Relay -> Motors
7.2V AND 9V battery to microcontroller, which drives servos, sensors, switches relay, and xbee radio
7.2V to custom acceleration sensor, which has built in logic to send a break signal at a fixed value

How I'd like to reorganize it, because these robots have reliability issues:

12V battery -> "X Board" -> voltage for boards, sensors, servos, and motor  (need 2 12V for motors, 1 9V maybe for arduino, 1 7.2V for the custome accelerometer, and several optional 5V for servos) that can be controlled by the microcontroller (which we intend to replace with an arduino of some flavor)

So I'm not really sure what such a board would be.  We have the ability to print our own circuit boards if necessary, but I hope such an item exists off the shelf.  What would the name of it be so I can search for it?

[Reply #1 on:]

What are best in your case would be DC to DC switching regulator modules. As you are working with battery power the efficiency of any voltage conversions should be as high as possible to extend battery duration, so simple linear regulators like 7805s and other voltage values are not the best choice, too much battery power wasted in heat dissipation in those type of voltage regulators.

So your task is to decide what output voltages you require and what the maximum current draw you require for each of those voltages and select the regulator modules to support that requirement. Note that you may want to use more then one regulator of the same output voltage so that say your servos are getting their +5vdc from a separate regulator then some other parts of your project that also require +5vdc, that way it might be easier to spread the current load among regulator modules rather then having to find a higher current rated one. Here is just a quick search list from E-bay showing many DC to DC switching regulators. Some are step up (sometimes call boost regulators) and others are step down (sometime called buck regulators). I've used several such from Asian E-bay sellers and have not yet had a problem with any of them and you can't beat the prices. Note that some of these modules have a pot adjustment that allows you to set the output voltage to what you need over a pretty large range, which is a very handy feature.

http://www.ebay.com/sch/i.html?_nkw=buck+regulator&_sacat=92074&_odkw=&_osacat=92074

Good luck;

Lefty

[Reply #2 on:]

Well the highest power draw is definitely going to come from 2 of these motors http://banebots.com/p/M5-RS550-12 which list 14.4V/85A max power draw.  Obviously I wouldn't want to run them at that for any length of time, but is there a way to narrow my search for boards that will handle that voltage, the moderate needs of a few smaller motors/servos, and the modest needs of a microcontroller and a few sensors.  It is a team of robots with slightly different configurations, but the motors and controllers are the same, and I'd like to use the same board across each for consistency.

[Reply #3 on:]

Well the highest power draw is definitely going to come from 2 of these motors http://banebots.com/p/M5-RS550-12 which list 14.4V/85A max power draw.  Obviously I wouldn't want to run them at that for any length of time, but is there a way to narrow my search for boards that will handle that voltage, the moderate needs of a few smaller motors/servos, and the modest needs of a microcontroller and a few sensors.  It is a team of robots with slightly different configurations, but the motors and controllers are the same, and I'd like to use the same board across each for consistency.

Well just as a general statement one wouldn't normally want or need to supply regulated DC voltage to motors running at 14.4V/85A, but rather just power them directly from lead acid or Li-Po battery packs via a suitably rated motor controller. Then all the other electronics requiring regulated DC would be powered via switching regulator modules that would also use the raw 14.4vdc as their input voltage.

Lefty

[Reply #4 on:]

Well the highest power draw is definitely going to come from 2 of these motors http://banebots.com/p/M5-RS550-12 which list 14.4V/85A max power draw.  Obviously I wouldn't want to run them at that for any length of time, but is there a way to narrow my search for boards that will handle that voltage, the moderate needs of a few smaller motors/servos, and the modest needs of a microcontroller and a few sensors.  It is a team of robots with slightly different configurations, but the motors and controllers are the same, and I'd like to use the same board across each for consistency.

Well just as a general statement one wouldn't normally want or need to supply regulated DC voltage to motors running at 14.4V/85A, but rather just power them directly from lead acid or Li-Po battery packs via a suitably rated motor controller. Then all the other electronics requiring regulated DC would be powered via switching regulator modules that would also use the raw 14.4vdc as their input voltage.

Lefty

Yes that would make a lot more sense wouldn't it...  I don't suppose there is a board that already combines a voltage regulator for the control circuit and the speed controller/relays for the brushed motors in one is there?

[Reply #5 on:]

I think by now you have an idea of the task and it's requirements, why not try to consolidate those idea's into a composite and submit that for discussion. There are a great many people here who have a vast composite amount of experience... and the people who argue against it also have input that should be considered, if only to "Not make that mistake" remember always that any input is generated from personal education and experience (or lack of it). "Stretching" in this manner is growth for you in the field of power control and the great part of learning is that you can never know when something picked up in search of something else might be useful.

Bob

[Reply #6 on:]

So I'm not really sure what such a board would be.

The best idea would be to separate the high power routes from the low power routes. Keep them separately powered.

If you have to power them from the same power source, use a diode + capacitor to isolate the low power boards from the motors and solder in thick copper wires for the ground.

[Reply #7 on:]

??? What ARE you trying to say. Did you read this?

Well just as a general statement one wouldn't normally want or need to supply regulated DC voltage to motors running at 14.4V/85A, but rather just power them directly from lead acid or Li-Po battery packs via a suitably rated motor controller. Then all the other electronics requiring regulated DC would be powered via switching regulator modules that would also use the raw 14.4vdc as their input voltage.

Lefty

Yes that would make a lot more sense wouldn't it...  I don't suppose there is a board that already combines a voltage regulator for the control circuit and the speed controller/relays for the brushed motors in one is there?

... this response was from the OP...

Bob