Cheap replacement for the Power Distribution Board

[AustinSchuh]

We are trying to get our 08 robot back up and running, and would like to avoid stealing the PD board from this year's robot. I'm pretty certain that the only thing that the PD board does for us that the 08 era electronics doesn't is provide the 24 volt boost converter for the CRIO, and 12 volts boost regulated for the radio.

Is there any easy way to replicate that functionality without buying the $190 breakout board?

Thanks

[DonRotolo]

Don't forget the 5 volts for the Camera - but you might not need that.

Is there a way to get 24 volts from 12? Yes. Google a "24 volt boost converter". Be sure it meets the specs you need in terms of current capability and voltage stability.

[EricVanWyk]

Just remember to be careful, and have someone with a good nose on hand in case you can't see the smoke plume.

Originally Posted by Don Rotolo

Don't forget the 5 volts for the Camera - but you might not need that.

The '09 Analog Breakout and the DSC have the same 12->5V regulator in it that the PD does.

[DonRotolo]

Originally Posted by EricVanWyk

The '09 Analog Breakout and the DSC have the same 12->5V regulator in it that the PD does.

I was thinking a 7805 would be easy enough, but that's a better way.

[AustinSchuh]

Originally Posted by Don Rotolo

Don't forget the 5 volts for the Camera - but you might not need that.

I doubt we will need that on our old robot. But if we do, I'll either use the 5 volts of the digital side car like Eric mentioned, or wire up a linear regulator. I've used linear regulators before for other projects, so I don't worry about how to use them.

[Al Skierkiewicz]

Austin,
If you are using IFI controllers then power distro is simply the fuse blocks that you can purchase from the same vendors as 2008 if you need them. If you are combining 2009 and 2008 sensors, or cameras then you will need to come up with some other solutions.

[AustinSchuh]

Originally Posted by Al Skierkiewicz

Austin,
If you are using IFI controllers then power distro is simply the fuse blocks that you can purchase from the same vendors as 2008 if you need them. If you are combining 2009 and 2008 sensors, or cameras then you will need to come up with some other solutions.

Al,

Ah, now that I go back and reread my initial post after reading your response, I can see how my post could be interpreted two ways.

Since the 08 robot's electronics got completely removed, we were thinking of wiring it up to to use the cRIO to test out new algorithms for control and just get it working again. We could almost just use the old fuse blocks which we have plenty of lying around, except that we need the 24 volt boost converter to power the cRIO.

Our backup plan definitely still is to use the 08 control system in it's entirety, controller and all.

After classes close out for the semester, I'm going to do some research and work on finding a suitable boost converter as suggested. Eric gave me some suggestions via PM, so I think I'm covered. Thanks everyone for your help.

[Greg McKaskle]

Note that this is coming straight from a SW guy, but since you don't care about being competition legal, and since the cRIO doesn't require 24V, but instead needs a minimum of 9 or so volts, another approach is to use a second battery instead of a PD. The cRIO draws very little power, and in the past we've run it for I believe four hours on a small lawnmower battery.

Greg McKaskle

[Al Skierkiewicz]

Originally Posted by AustinSchuh

Al,

Ah, now that I go back and reread my initial post after reading your response, I can see how my post could be interpreted two ways.

Since the 08 robot's electronics got completely removed, we were thinking of wiring it up to to use the cRIO to test out new algorithms for control and just get it working again. We could almost just use the old fuse blocks which we have plenty of lying around, except that we need the 24 volt boost converter to power the cRIO.

Austin if you just tether then any of these options should work fine. Wireless, the access point becomes the biggest problem. So using Greg's option you could also add a third battery for the wireless. I am thinking this through, but my first guess is to put the batteries close together, and tie the negative leads together to prevent circulating currents from running the source voltage up and down for the cRio and the wireless.

[Russ Beavis]

Greg,
Doesn't the FRC cRIO require a higher minimum supply voltage (ie 19V) than the standard cRIO line? I thought that was one of the differences between the cRIO setups using separate controllers and the integrated chassis/controller being used by FRC.

Russ

[Joe Ross]

Originally Posted by Russ Beavis

Greg,
Doesn't the FRC cRIO require a higher minimum supply voltage (ie 19V) than the standard cRIO line? I thought that was one of the differences between the cRIO setups using separate controllers and the integrated chassis/controller being used by FRC.

According to the cRIO-FRC Operating Instructions that is the case.

[EricVanWyk]

My understanding is that it is only guaranteed to work over the 19-30V range. It might work lower, but you are on your own. The boost supply was designed to not test those bounds, but independent projects can attempt what they see fit and live with the consequences. I've definitely seen the cRIO operate well below 19V, but I wouldn't guarantee that it works 100% of the time.

However, if Greg (Mr. NI) says it will work, I'll believe him. He'd know much better than I would.

[SteveJanesch]

For the 24V supply, I assume you could also connect two 12V batteries in series. You'd need to connect the negative terminal of the stack to the negative rail of the robot somewhere (like the old ground lug) - you wouldn't want a floating 24V powering the cRIO. If all you're running from the stack is the cRIO, it should last for hours.

You'd probably want to connect the stacked batteries in some way to easily disconnect them for recharging - I haven't thought that part of it through.

- Steve

[Greg McKaskle]

As I mentioned at the beginning, I'm just a SW guy -- with a EE minor, but that was a long time ago. I know for certain that we have run cRIOs on a single 12 volt battery, but I can't be certain that the cRIO was stock. They may have modified the power supply, or they may have simply verified that it'd run to the 9 or so volts that I remember.

I certainly am not suggesting any modifications to the cRIO, and I'll take any EE input over my own when it comes to power.

Greg McKaskle

[Al Skierkiewicz]

How about we just stick with the 24 volt requirement for all discussions. That will simplify matters for the majority of the people who read these posts.
Yes, you can stack (series wire) two 12 volt batteries to produce the 24 volt requirement. However, everyone should note that the load on any given battery will change it's terminal voltage dependent on the current supplied to the load and the internal resistance of that battery. It is not uncommon for our robot batteries to be pulled below 8 volts during normal running conditions. That is why the 8 volt trip point was selected in the IFI controller and why Eric and Russ designed the 24 volt power in the new 2008 PD to maintain output below 5 volts. The internal resistance of our batteries is typically 11 mohm and can deliver over 600 amps at full charge. CIM motor stall current is 129 amps so four or more motors in stall can draw down the terminal voltage significantly.