Prefabbed Drive Train

[John16]

We recently purchased an AndyMark nano-tube drive chassis. We've hooked up 4 CIMs to it, two to drive the rear four wheels, and two for the front two wheels. When reversing directions quickly, we seem to be able to drop the voltage low enough to reset the router, but only with either of the two front motors connected. Disconnecting the two from, we can run all day without the issue. Any ideas why this is happening, and how to overcome it?

We've previously used four CIMs in our drive train before, but with chains. We weren't sure if the previously not experienced sudden current draw was coming from the almost zero lag of the gear system.

We greatly appreciate any and all assistance in understanding this. Thank you.

[DarrinMunter]

Are you using the 12 to 5 volt DC to DC converter?
This converter gets plug in to the PD at the regulated 12V output.

[Gregor]

Do you have the router plugged into the 5v port of the PD board, or are you using the dedicated 12v port of the PD board (not the normal 12v ports on the side), with a 12v-5v dc-dc convertor (http://www.current-logic.com/shop/images/DC_DC_Converter_car_small.jpg) to step down to 5v?

[Mark McLeod]

Is your radio power wired to the special 12v protected power supply?
Voltage dips are more likely to affect the radio when it's wired to a regular WAGO connection (incorrect).

Take a look at your Driver Station log to see the voltage graph. How low is it going?

Certainly, stalling 4 CIMs by a quick reversal can draw the voltage quite low, but the radio is unlikely to brown out from it.

[magnets]

There's a million things that could cause this.
Here's a list of the most probable
Is you battery charged?
Have you tried a different battery?
Do you have the radio wired correctly?
Is there too much resistance in the drive train?
Did you lubricate your gears?
Do you have an electrical problem?
Is there a loose connection?
Do you have a weird frame short issue or grounding issue?
Have you measured resistance from ground to your frame, and was it anything other than infinity/no connection?

[John16]

We are using the dedicated 12V port on the PDB, along with the 12v-5v dc-dc converter.
There are no shorts to the frame.
Our lowest reading with a DMM directly from the Talons power side (not motor side) was 8.7V. A very noticeable dip which would give serious indication we are experiencing a huge current draw, which is why I'm here.
Gears are lubed
Yes, battery was fresh, each time.

[MichaelBick]

How old are your batteries?

[DarrinMunter]

Recheck the tightness of all the bolts, screws and nuts from the battery to the circuit breaker to the PD. Loose connections will cause a drop in voltage under heavy loads, and show full voltage when your robot is at a stand still.

[Ether]

We recently purchased an AndyMark nano-tube drive chassis. We've hooked up 4 CIMs to it, two to drive the rear four wheels, and two for the front two wheels. When reversing directions quickly, we seem to be able to drop the voltage low enough to reset the router, but only with either of the two front motors connected....

We've previously used four CIMs in our drive train before, but with chains. We weren't sure if the previously not experienced sudden current draw was coming from the almost zero lag of the gear system.

Are you sure the router is resetting? Can you describe the exact symptoms?

What motor controllers did you use in the previous drivetrain and the present one?

[ErvinI]

This sounds very similar: http://www.chiefdelphi.com/forums/showthread.php?t=98128

There were multiple issues found that could have led to brownouts on that robot. However, the main one on that robot seems to be a non-issue on yours.

From that thread:
I was working with / trying to help these guys yesterday at Brunswick Eruption. There were numerous problems being identified and we were trouble shooting them one at a time. This is as far as were able to get.

1) The ground wasn't firmly attached to the stud on the PD. Fixed
2) One Gear Box was loose and wobbling. Fixed
3) We measured the power drop between the studs on the PD with a multi-meter when they changed directions it went from 12volts to 8volts and lower.
We recommended fully charged batteries.
4) I didn't check if the CRIO rebooted, but the DLINK rebooted every time.
5) They also have the D-Link powered by a 20AMP circuit like James posted previously.
6) Lastly, I'm wondering if direct driving Mechanum Wheels using 4 - CIMPLE Boxes wasn't enough of a mechanical reduction and hence cause too much draw.

On another note, do radio brownouts actually occur at 8.7 V? I thought it was 6V or lower; I remember our motors getting dangerously close to 6 V last year with no brownouts, but it's been sometime.

[Nirvash]

On another note, do radio brownouts actually occur at 8.7 V? I thought it was 6V or lower; I remember our motors getting dangerously close to 6 V last year with no brownouts, but it's been sometime.

The radio should not be browning out at ~8 volts, the 12 volt regulated output on the PDB is rated for a minimum input of 4.5 volts.

[John16]

I thank you all for your replies. There are no loose nuts (besides me).
We are using talons.
We know it "shouldn't" be browning out the radio, but it is.
I just received some information from a teammate I need to process. It may shed more light on this.

[John16]

Well, seems that one of our members is positive our digital sidecar is plugged into the dedicated port instead of the 12v-5v converter.

We will try swapping those this saturday and see if that fixes our issue.

[gpetilli]

When reversing directions quickly, we seem to be able to drop the voltage low enough to reset the router, but only with either of the two front motors connected. Disconnecting the two from, we can run all day without the issue.

Did you try running only with the front wheels connected to see if there is a 4 CIM issue or if there is an electrical problem with the front wheels? Is the router mounted near a front CIM or its wires (I like to twist the CIM wires to reduce radio interference).

[Alan Anderson]

Well, seems that one of our members is positive our digital sidecar is plugged into the dedicated port instead of the 12v-5v converter.

I saw more than one robot miswired that way last year. One of them was at the Championship, having passed inspection at two previous competitions. I don't know what could be improved in the documentation to make it more clear where everything should get its power.

[Chris_Ely]

Well, seems that one of our members is positive our digital sidecar is plugged into the dedicated port instead of the 12v-5v converter.

According to the Power Distribution Diagram (http://www.usfirst.org/sites/default/files/uploadedFiles/Robotics_Programs/FRC/Game_and_Season__Info/2013/ElectricalLayout.pdf), the digital side car should be plugged into a standard 12V output on the power distribution board. The radio should be plugged into the 12V-5V converter, which is plugged into the regulated 12V out on the power board.
Check the lights on the sidecar. All three should be brightly lit.

[John16]

I thank you all greatly for your input. It appears that we had newer teammates wiring the drive chassis and they weren't checked to make sure we had it right. With the radio connected to the regulated 12v output from the PD we no longer have the brownouts.

Alan Anderson, I don't think anything needs to be done to make the documentation clearer, we just need to make sure newer members know about it and veteran members need to make sure it's followed. An oversight where we all assumed everyone else was doing it right.

[Ether]

With the radio connected to the regulated 12v output from the PD ...

The radio is supposed to be connected to the 12-to-5 volt converter, which in turn is connected to the regulated 12v output of the PDB.

[John16]

It is, I was just choosing to not get overly detailed. The radio is connected to the 12v regulated output of the PD VIA the 12v-5v converter...

[DonRotolo]

Alan Anderson, I don't think anything needs to be done to make the documentation clearer, we just need to make sure newer members know about it and veteran members need to make sure it's followed.
What? You mean now we have to actually read the documentation? That's not fair!:rolleyes:

[Uniwersel]

What? You mean now we have to actually read the documentation? That's not fair!:rolleyes:

Well, maybe. ::rtm::