Turret brakes

13feb18

How the brakes work
Debugging brake problems

180211: turret brakes fail. Current sensor not reaching correct current level.

How the brakes work (top)

There are 2 turret motors (master and slave). Each motor has a brake. The brakes are spring loaded to the on position. Before moving the turret these brakes must be released (pulled back). This is done using solenoids. A current monitor is used to measure the current through each solenoid. When the current rises above a preset value, the brakes are "released".

Debugging brake problems

The monif program can be used to debug brake problems. It updates once a second. The image below is a screen shot of the program running:

monif screen shot

When a brake problem occurs, it will typically show up in the TurFlt line with BrkFail.

The image below shows the turret brake schematic:

Ref	monif Line	bits (cntFrom0)	MonIf label	Notes
A	TurOLs	B8	BrkOffCm	Brake off command. Analog output to release brakes.
B	TurDI2	B11	BrkOffCM	Monitors the brake off command going to the releaseCoil.
C	TurDI3	B7	BrkOffMon	Monitors the output of the brake current sensor going to the IsReleasedCoil has reached the correct current level.
D	TurDI1	B12	BrkOffMn	Monitors that the IsReleasedCoil is working correctly
E	TurDI3	B14	BrkOffCmdc	Monitors that the ReleaseCoil is working properly.
F	TurDI3	B6	IlKey	Monitors the turret interlock key. If set, then turret can not be moved

Debugging steps.

IlKey is not active. F. TurDI3 IlKey is not active.
Brake off being requested: A. TurOLs BrkOffCm
Brake off analog output working: B. TurDI2 BrkOffCM

If not, maybe the analog output is bad, or an opto isolator for the input

Check that release coil is working: E. TurDi3 BrkOffCmdc
Check that the current in the brake current sensor has risen to the proper level. C TurDI3 BrkOffMon.

If not, check the opto isolator, and the current sensor

check that the IsReleasedCoil is working: D. TurDI1 BrkOffMn.

If any of the inputs are not working, first check the opto isolators for that bit ( since they tend to fail first)..
Note that the specified bits count from 0, not 1.

processing: x101/180212/turretbrakes.xcf (used by gimp program).

180211: brake fail, current sensor level.

On 11feb18 there were turret brake failures.

Turret status during brake failure (.ps) (.pdf)

19.523. Turret stopped, reset, and then motion requested (first dashed line)
the TurFlt occurred at 19.5236 (2nd dashed line).
Page 5: BrkOffCM. goes low then hi, so analog command requesting brake off.
Page 4: DI1

BrkOffCm: goes low, then high, RequestCoil is working
BrkOfMn: goes low, but does not go high.

so IsReleasedCoil is not activating.

Page4:DI3

BrkOffMc: stays low. This is the input to the IsReleasedCoil

So the brake current sensor is not reaching the required current to release the brakes.

The current sensor was readjusted, and will be replaced.

processing: x101/180212/turbrkfail.pro

page up: turret

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