Gecko G3 0 Series User manual

Gecko G3x0
Error
Reset
Controller
Relays included version
Rev 2.

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 1
All the standard legal disclaimers that have ever been written apply to this document.
If you are not completely proficient in electrical wiring and familiar with local
ordinances, you should not proceed.
Design Theory
The Gecko G320 and G340 controllers are fabulous devices, but have one minor little
annoyance - the Error/Reset pin. The operation of this pin is somewhat confusing, and the
usage even more so.
The newest version of the Gecko 3x0 devices ease the use of this pin by allowing a person to
wire all the pins in a system together, but this is still, in my opinion, an incomplete and
inflexible solution.
Looking at the various circuits available from a number of sources, I decided that none of them
precisely suited my needs and so decided to create yet another design. Considering that the
problem was mostly one of logic and only partly electronics, I decided to use a microcontroller.
My design goals were these.
•Automatically provide the 5 second reset required at powerup.
I don’t think, in this day and age of electronics, I should have to stand around and wait
for a light to go off.
•Fault all the axes should a single active axis fault.
If something bad happens such that an axis faults, it’s obviously important to turn
everything off. The part may still be rescued and possible damage to the machine or
tooling is eliminated.
•Provide a means to disable all the motors without having to resort to a poweroff.
Turning on big power supplies, like those found in servo supplies, puts a strain on many
of the components in the supply. I wanted a means of resetting/disabling things without
the “shock” of simply turning it off.
•Provide a means to disable a single axis without disturbing the fault detection logic.
Sometimes I like to combine CNC movement with manual adjustment. For example, on
a piece of material of unknown composition, I may manually adjust the Z axis until I’m
confident of the depth of cut.

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 2
•In the event of a fault, indicate which axis caused the fault.
If something bad happens to an axis, I want to know which axis. The Gecko gives this
information, via an LED turned on inside the case. I want to see it outside the case.
•Allow an EStop input to disable both the motors (via relays) as well as disabling the
Geckos.
An external EStop switch should be a part of every servo system. This switch should be
at a minimum a Big Red Button within easy reach. Much better still is a Big Red Button
combined with limit switches on each axis.
When stepper electronics fail, typically the motor refuses to turn. The most common
form of servo electronics failure sends the motor running at maximum speed.
This is the reason for relays. Should the servo electronics fail in such a manner, simply
saying to the Gecko (via pin5) “please stop” will not work, causing extreme badness.
However, for those people who, for whatever reason, choose not to add relays, the
EStop input will also disable the Geckos via pin5.
•Send a signal to the controlling PC should a fault occur.
The PC may have other apparatus connected to it besides just the servo motors. If
something bad happens, the PC should be informed.
The result of these ruminations were the GERC, a small PCB that did all of the above.
I feel quite strongly that relays should be part of every servo system but found that some
people were put off by the (modest) additional wiring requirements to incorporate them.
Others were somewhat discouraged by the requirement to source and wire a separate 5 volt
power supply.
So a second product was developed, the GERC_RLY. This device is an All-In-One version of
the original GERC with relays, protection diodes, dynamic braking resistors and power supply
built in.

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 3
Connecting the GERC_RLY
J1 – Power
Perhaps the most important connector on the PCB, J1 pin2 is used to connect the DC common
of the GERC_RLY (more commonly - if less correctly - known as “ground”) to the DC common
(ground) of the motor power supply.
While J6 to J9 (the relay connectors) have connections to the motor supply ground, this
connection must also be made, as the relay connections are completely separated from the
logic connections.
Power for external devices
A total of 200 milliamps (ma) of current is available for powering external devices.
An unregulated source of approximately 12 volts DC is available between J4 pin 2 (+) and J1
pin 2 (0).
A regulated 5 volts is available from J1 pin 1 (+) and J1 pin 2 (0).
The two sources may be used at the same time, but at no time must the total consumption
exceed 200 ma.
J2 – EStop output
The EStop output allows the GERC_RLY to alert the controller (typically a PC) or an intelligent
“break out” board that something bad has happened. Technically, it is the contacts of a single
pole double throw (SPDT) relay. As such, it may be wired in two manners.
1. the contacts are closed for normal operation and open in the event of a problem.
Connections would be made using pins 2 and 3. Alternately,
2. the contacts are open for normal operation, and close in the event of trouble. In such a
case, connections would be made using pins 1 and 2.
If there is a choice (as determined by the controller software or the breakout board), it is
recommended that option 1 be chosen.
Example: Direct connection to a parallel port
Assuming that the controller has a PC sending step and direction pulses through a parallel
port, the recommended connection is a follows.
J2 pin 2 would go to the Ground connection of the parallel port.
J2 pin 3 would go to one of the inputs pins of the parallel port.

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 4
Consult the documentation for the controller software to determine which pin the software
expects for an EStop signal.
For correct operation, the EStop pin on the PC parallel port must be actively pulled high
via a resistor. The GERC_RLY does not “make it go high”.
Thankfully, the input electronics of most parallel ports already do this.
Finally, don’t forget to configure the software in the PC for an active high EStop signal.
J3 - Error/Reset connections
This is how the GERC_RLY communicates with the Geckos.
Using figure 1 (below) as a guide, connect a wire from the X Y Z and A points of J3 to Pin 5 of
the relevant Gecko. (Four Geckos, four wires)
Note: These inputs are a direct, unprotected connection to the microcontroller. Do not
connect these inputs to anything except the Error/Reset pin of a Gecko G3x0.
J4 - EStop Switch
The EStop switch input is a designed to be connected to an external “Big Red Switch”, located
in such a position that it is easy for the operator to activate it should the need arise.
This switch must be closed for the GERC_RLY to operate. When the switch contacts open,
the GERC_RLY will stop motor activity (by first placing the Geckos into reset and then
removing power to the Geckos).
X
X axis motor
J3
X axis Gecko
GERC
Pin 5
Figure 1

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 5
Should the switch fail, the GERC_RLY will not allow the motors to turn. Should the wires
leading to the switch be cut (by hot swarf, for example), the GERC_RLY will not allow the
motors to turn.
The GERC_RLY is shipped with a wire jumpering the EStop input, for testing purposes only.
As a minimum, an external switch really should be connected. It is strongly recommended that
EStop limit switches also be wired into the EStop loop, as shown below in Figure 2.
It is not enough to rely on limit switches wired to the controller. Should the Geckos fail
such that the motors run full speed, limit switches wired to the controller will be
ineffective.
The EStop switch carries relay power, and as such, the contacts cannot be shared with any
other device.
If an EStop switch is to be used to turn off the lathe or mill motor, for example, as well
as turning off the Geckos, then the EStop switch must be a multi pole device.
EStop Override
When limit switches are wired into the EStop circuitry (as recommended above), the
table/knee/quill will have to be moved to a position such that the limit switch is no longer open.
On a machine with handwheels, this presents no problem. On fully automatic machines, that
is, machines with no handwheels, a Catch-22 situation arises whereby the table can only be
moved by the Geckos and the GERC_RLY will not allow the Geckos to operate until the table
has moved.
X limit switch Y limit switch Z limit switch
Figure 2
J4
EStop switch
Figure 3
GERC EStop
J4
Other EStop device

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 6
For such machines, an EStop Override switch is required to “trick” the GERC into thinking that
all is well. This must be a normally open switch and really should be a momentary switch. It
must also be placed within easy reach of the keyboard, as you’ll be holding this Override
switch down with one hand will jogging via the keyboard with the other.
The actual series of operations to clear such an event is as follows.
1. Press and hold the EStop Override switch.
2. Reset the GERC_RLY by toggling the AllStop/Reset switch (as described below)
3. Reset your controller program (if required)
4. Jog the offending axis
J5 110 VAC power input
The GERC_RLY has an onboard power supply, but needs 110 Volts AC. This must be
supplied through a power switch and fuse, in accordance with local regulations. It is the outer
two connections that are used; the inner terminal is used for isolation only. A suitable value for
a fuse would be 1 amp, quick blow. Typical current consumption is 100 ma.
J6-9 Relay Connections
J6 X axis power connector
J7 Y axis power connector
J8 Z axis power connector
J9 A axis power connector
These connectors are wired to the relay contacts.
DC power from the motor’s power supply comes in to pin 1 of the connector, and then to the
Normally Open relay contact.
The Common relay contact is attached to the connector’s pin 2, and then to the Gecko’s pin2.
The Normally Closed relay contact is connected to a power resistor, used for dynamic braking.
The other end of this power resistor goes to pin 3 of these connectors, which is then connected
to the power supply negative (aka, “ground”).
EStop Switch Limit Switches EStop Override Switch
Figure 4
J4

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 7
The GERC_RLY, upon power up, examines the state of the axis enable switches (more on this
later) and depending upon which switches are “up”, closes the appropriate relay contacts,
which then powers the appropriate Gecko(s).
Should a Gecko fault or an EStop condition be detected, all relays are opened. Power is now
removed from the Gecko(s), and a power resistor connected across the motor terminals. (This
connection is actually through the Gecko, not directly to the motor, but the nature of the Gecko
output stage is such that this is the correct way to do this.)
Here are the circumstances under which the GERC_RLY will disconnect power to the Gecko.
1. The control switch for an axis is set to disable.
2. An axis faults. When one axis faults, the GERC_RLY will disable all the axes.
3. The EStop switch is pressed.
The GERC_RLY will disable the axes by pulling the Error/Reset pin (pin 5) of the Gecko low
and by removing power from the relays.

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 8
Usage
Switches:
There are five switches on a GERC_RLY. The first four are used to enable or disable the X, Y,
Z, A axes. They must be up (pointing to the LEDs) to enable an axis.
The rightmost switch is the AllStop/Reset switch. It must be up as well for things to operate.
Down is All Stop (no matter what the state of the other four switches)
Down, then up again, is Reset.
Normal condition, then, is all switches UP.
LEDs:
There are four LED conditions.
Enabled axis
When an axis is ENABLED, the LED for that axis is ON steady.
With all axes enabled, all LEDs are on steady.
With all axes disabled, no LEDs are on.
Normal operation, then, is all LEDs on.
Reset
Any time the unit is reset, the LED for an enabled axis will blink slowly for 5 seconds or so. If
all axes are enabled, all the LEDs will blink (in unison). During this time, the Geckos are being
reset, and the fault LEDs on the Geckos (hidden away inside your chassis where you can’t see
them) should go out.
Two things cause a reset.
1. Power turned on.
2. Toggling the AllStop/Reset switch.
Axis fault
Should a Gecko detect a fault condition on an axis during normal operation (things working
fine), the LED for that axis will blink quickly.
A single blinking LED indicates a faulted axis.

GERC_RLY Rev 2 Wiring and Usage manual
January 9, 2007 9
The GERC_RLY will never show more than one axis faulted, even though more than one axis
may have faulted. The instant an axis faults, the GERC_RLY immediately disables all the
axes.
EStop event
When an EStop event occurs, all the LEDs blink rapidly until the EStop condition is cleared.
Once the EStop condition is cleared, the LEDs then blink in sequence.
X LED, then Y LED, then Z LED, then A LED, then X LED again ...
Note: Once the EStop condition is cleared, the GERC_RLY requires a reset, either by
toggling the AllStop/Reset switch or by a power cycle, before the motors will again be
allowed to operate.
This is a safety measure, so that a machine stopped by an EStop event does not
unexpectedly begin to move again.
Normal Operation at Powerup:
Assuming all switches are up … all axes enabled …
All GERC_RLY LEDS blink in unison
Within 5 seconds, the Gecko LEDs go out.
Just after 5 seconds, the GERC_RLY LEDs stop blinking and remain on constantly.

Date: January 28, 2007 Sheet 1 of 4
Size Document Number REV
B GERC_RLY 2
Title
GERC Including Relays
are ELECTRONICS
Relays
RELAYS.SCH
ES_In
X_In
Y_In
Z_In
A_In
Closed for normal operation
EStop Input
VEStop
12
J4
Connector for external ESTOP switch
VCC 3
RESET 2
GND 1
U1
DS1233
+5
+5
V
D
D
2
V
S
S
4
RTCC
1
MCLR
28
RC0
18
RC1
19
RC2
20
RC3
21
RC4
22
RC5
23
RC6
24
RC7
25
OSC1
27
OSC2/CLKOUT
26
RA0 6
RA1 7
RA2 8
RA3 9
RB0 10
RB1 11
RB2 12
RB3 13
RB4 14
RB5 15
RB6 16
RB7 17
U2
+5 C3 - C6
Inputs from G320s
Xin
Yin
Zin
Ain
R6 - R9
1
2
3
4
J3
IN1
1 IN2
2 IN3
3 IN4
4 IN5
5 IN6
6 IN7
7 IN8
8 VS
9
OUT1 18
OUT2 17
OUT3 16
OUT4 15
OUT5 14
OUT6 13
OUT7 12
OUT8 11
COM CATH 10
U3
ULN-2803A
Xout
YOut
Zout
Aout
VEStop
Xerr
Yerr
Zerr
Aerr
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
RP1
100r x 8
Xstop
Ystop
Zstop
Astop
Allstop
Es
Es
ISO1
4n35
R5
750r
1
2
3
X1
4MHZ Ceramic Res
PIC16f57
PIC16c55a
R1
470r
R2
470r
R3
470r
R4
470r
Xstop
Ystop
Zstop
Front Panel
FPANEL.SCH
S1
S2
S3
S4
S5
XLED
YLED
ZLED
ALED
GND
+5
1
2
3
4
5
6
7
8
RP2
4k7 x 7
Xstop
Ystop
Zstop
5
10
8
1
16
K5
RELAY
1
2
3
J2
Astop
Allstop
Es
Pullups for switches
+5
Astop
Allstop
+5
VEStop
Power
POWER.SCH
VEStop
Q1
2n2222
EStop Output
1
2
J1
Power (to external electronics)
+5

Date: January 28, 2007 Sheet 2 of 4
Size Document Number REV
A GERC_RLY 2
Title
Front panel for G320 error/reset Rev 2
are ELECTRONICS
S1
SW SPDT
Front Panel PCB
D1
LED
+LED
D2
LED
+LED
1
2
3
4
5
6
7
14
13
12
11
10
9
8
J12
S2
SW SPDT
S3
SW SPDT
S4
SW SPDT
+LED
+LED S1
S2
S3
S4
S5
1
2
3
4
5
6
7
14
13
12
11
10
9
8
J11
XLED
YLED
ZLED
ALED
+5
GND
Connector on main PCB
D3
LED
S5
SW SPDT
D4
LED
+LED
Note: SPST throw switches can also be used

Date: January 28, 2007 Sheet 3 of 4
Size Document Number REV
B GERC_RLY 2
Title
GERC Including Relays - Relays
are ELECTRONICS
R10
4r7
VRelay
ES_In
A_In
VRelay K1
P&B T90
D5
50sq100
0
To Motor
To Power
1
2
3
J9
0
To Motor
To Power
1
2
3
J8
VRelay K2
P&B T90
R11
4r7
Z_In
R12
4r7
D6
50sq100
0
To Motor
To Power
1
2
3
J7
VRelay K3
P&B T90
D7
50sq100
Y_In
VRelay K4
P&B T90
R13
4r7
D8
50sq100
0
To Motor
To Power
1
2
3
J6
X_In

Date: January 28, 2007 Sheet 4 of 4
Size Document Number REV
B GERC_RLY 2
Title
GERC with relays - power supply
are ELECTRONICS
Heatsink
VEStop
1
2
3
J5
6
4
3
1
7
9
10
12
T1
MICROTRAN
D9
1n5820
D10
1n5820
C7
220u
C10
220u
C8
220u
IN
1 OUT 3
G
N
D
2
U4
LM7805
VCC +5
C1
.1u
C2
.1u
110V In