A real puzzle - Electromechanical fault

[Cal578]

The 12V-5V converter is good to about 7V input.

[Mark McLeod]

The two PDP protected 12v & 24v outputs are good down to about 4.5v, maintaining their 12v/24v.
The 5v PDP output get cut off at around 5.5v.
Beware sharp sudden spiky dips at low voltages.

See Power Distribution Board.pdf, pages 6 & 7 Specifications for minimum voltages for the 24v protected supply, 12v protected supply and 5v outputs.

P.S.
Correction: the regular 12v outputs do not get cut off at low voltage. They follow the battery on down.
But, something cuts controlling PWM/relay outputs at less than 6v, so the effect is the same.

[Joe Johnson]

Originally Posted by Mark McLeod

The two PDP protected 12v & 24v outputs are good down to about 4.5v, maintaining their 12v/24v.
The other PDP outputs get cut off at around 5.5v.
Beware sharp sudden spiky dips at low voltages.

See Power Distribution Board.pdf, pages 6 & 7 Specifications for minimum voltages for the 24v protected supply, 12v protected supply and 5v (as well as all regular 12v-direct battery) outputs.

Thanks. I should have looked for the manual myself.

In practice, do they have caps on the inputs to survive small spikes that dip below these values or does noise make the radio go dark?

Also, have people had any success monitoring battery voltage and then modifying motor outputs to prevent such brown outs? It seems like it would be reasonably straight forward: when battery voltage dips below X find the largest users of current (probably wheel motors) and scale their output back until the battery voltage recovers. With a reasonably fast loop time, I suppose that we can keep from browning out in the first place (you'll lose power on the motors but you stay connected -- seems like a bargain worth making).

Joe J.

[Mark McLeod]

Small spikes aren't a problem, I see a lot of brown outs that don't affect the radio or cRIO forcing them to reboot.
One toe below 4.5v and the protected outputs are gone though, and I've seen that happen from sharp spikes.

Monitoring the battery voltage ourselves in code has worked out when we have had a big draw device, such as a flywheel.
The FPGA code also monitors the battery voltage and reacts when it drops below a threshold voltage, disabling the PWM/Relay outputs.

P.S. I made a correction to my earlier statement, because I'd said that the PDP cuts the regular 12v outputs. It doesn't, but the effect is the same when the PWMs get disabled.

Attached is the circuit diagram.

[msimon785]

While I'm sure you've checked this, it could always be a problem: could you be running the two CIMs in each CIMple box against eachother?

[kevin.li.rit]

Originally Posted by msimon785

While I'm sure you've checked this, it could always be a problem: could you be running the two CIMs in each CIMple box against eachother?

They are running 4 cims on 4 cimpleboxes... So I don't think that's the case.