Remote control for welders and method therefor

A method and system for remotely controlling operational parameters of welders by communicating over a welding cable thereof with a remote device electrically coupleable between a workpiece and an electrode holder of the welder. The operational parameters include remotely enabling and disabling the welder, remotely choking the engine thereof, remotely controlling coarse and fine current adjustment, and remotely controlling other parameters otherwise controllable from a control panel of the welder. The remote device having one or more operational parameter signal circuits electrically coupleable between the workpiece and the electrode holder for producing unique operational signals on the welding cable, a sensor circuit that detects the operational signals and produces corresponding operational sense signal in response thereto, and an operational control circuit that actuates operation controls corresponding to the operational parameters on the control panel of the welder in response to the operational sense signals.

BACKGROUND OF THE INVENTION 
The invention relates generally to welders, and more particularly to 
systems and methods for remotely controlling welders using a remote device 
interposable between a workpiece and an electrode holder and communicating 
along the welding cable to control various operational parameters 
otherwise controllable locally from a control panel thereof. 
Welding machines, or welders, are known generally and used widely for a 
variety of welding applications. Engine-driven welders include a 
combustion engine-driven generator that provides an electric welding 
current, and static welders obtain welding current from an electrical 
converter connected to an electrical power supply line. The welding 
current and other operational parameters of these and other welders are 
generally selectable and controllable locally from a control panel 
thereof. 
In the Bobcat.TM. 225G Plus engine-driven welder, available from Miller 
Electric Mfg. Co., an Illinois Tool Works Company, Appleton, Wis., for 
example, the control panel includes AC/DC selects, polarity reversing 
selects, and coarse and fine current adjustment controls. The control 
panel of the Bobcat.TM. 225G Plus engine-driven welder also includes 
engine choke, start, run/off and low idle controls. Other welders may 
control some or all of these operational parameters. Static welding 
machines for example do not require engine choke and idle controls. Other 
operational parameters include wire feed and auxiliary power controls. 
In many applications, especially engine-driven welder applications, welding 
is performed at a site remote from the welder and the control panel 
thereof. For convenience, it is known to control a limited number of 
welding parameters remotely from the control panel. Namely, coarse and 
fine current adjustment. U.S. Pat. No. 4,216,367 entitled "Wireless Remote 
Control for Electric Welder" issued Aug. 5, 1980 to Risberg and assigned 
commonly herewith, for example, discloses a device for remotely 
controlling weld current in an engine-driven welder to precise percentages 
of a current value selected previously at the control panel thereof. U.S. 
Pat. No. 4,216,367 discloses, more particularly, an adjustable rheostat 
temporarily disposable between a weld stick and workpiece to generate a 
calibrating current, which flows through the welding cable. The 
calibrating current is sensed by a current transformer and compared to a 
previously set and stored welding current reference, which is adjusted 
automatically after a slight delay to a new desired weld current value. 
The present invention is drawn toward advancements in the art of welders, 
and more particularly to systems and methods for remotely controlling 
various operational parameters of welders including engine-driven and 
static welders. 
The inventors of the present invention recognize the desirability of 
remotely starting and stopping welders, particularly engine-driven 
welders, in addition to or besides controlling weld current. More 
particularly, remotely starting and stopping welders without any 
additional cables between the remote site and the control panel thereof. 
Remote welder control eliminates the necessity of walking back and forth 
between the control panel and the work-site, which may be located a 
significant distance therefrom. In some applications, moreover, a 
plurality of welders are arranged in large banks of welders, which are 
operated by many welding operators at remote locations. The operators may 
not know, and it may be very difficult to ascertain, which welder is 
coupled to a particular welding cable. The advantage of remotely enabling 
and disabling the welder under these circumstances is self evident. Remote 
enabling and disabling engine-driven welders is desirable also for 
reducing engine and generator operation time, thereby extending the 
useable life thereof as well as other components of the welder. The known 
prior art however does not teach remote enabling and disabling of welders. 
It is therefore an object of the invention to provide novel methods and 
systems for remotely controlling welders, and more particularly for 
remotely controlling operational parameters thereof by communicating over 
a welding cable with a remote device electrically coupleable between a 
workpiece and an electrode holder. 
It is also an object of the invention to provide novel methods and systems 
for remotely controlling at least one, and preferably more than one, 
operational parameter of welders otherwise controllable locally from a 
control panel thereof, including remotely enabling and disabling the 
welder, remotely choking engine-driven welders, remotely controlling 
coarse and fine current adjustment, remotely reversing current polarity, 
among other operational parameters thereof. 
It is a more particular object of the invention to provide novel methods 
and systems for remotely controlling welders having generally a welding 
cable and an electrode holder for supplying weld current to a workpiece, 
and one or more operation controls for locally controlling corresponding 
operational parameters from a control panel thereof. The novel methods and 
systems include a remote device having one or more operational parameter 
signal circuits electrically coupleable between the workpiece and the 
electrode holder for producing corresponding unique operational signals on 
a welding cable, a sensor circuit for detecting the operational signals 
and producing corresponding operational sense signals in response thereto, 
and an operational control circuit for actuating corresponding operation 
controls of the welder in response to the operational sense signals, 
thereby remotely controlling operational parameters of the welder 
corresponding to the unique operational signals produced by the remote 
device on the welding cable. 
It is another more particular object of the invention to provide novel 
methods and systems for remotely controlling welders with a remote device 
having one or more constant current source circuits electrically 
coupleable between the workpiece and the electrode holder for selectively 
producing one or more corresponding unique operational signals on the 
welding cable. It is a related object of the invention to provide a 
battery powered remote device having one or more constant current source 
circuits coupled to a timer circuit that produces unique intermittent 
operational signals on the welding cable, whereby the intermittent 
operational signals reduce battery power consumption. 
It is still another more particular object of the invention to provide 
novel methods and systems for remotely controlling welders having a 
current transformer sensor circuit for detecting operational signals 
produced by an alternating carrier wave on the welding cable. 
It is a further object of the invention to provide novel methods and 
systems for remotely controlling welders with a remote device electrically 
coupleable between a workpiece and an electrode holder, wherein the remote 
device includes a first electrode coupleable to the workpiece and one or 
more second electrodes coupleable to the weld stick, or electrode holder, 
for generating unique operational signals on the welding cable, whereby 
the second electrodes are readily and accessibly contactable by the 
electrode holder to selectively remotely control corresponding operational 
parameters of the welder. It is a related object of the invention to 
magnetically and electrically couple the first electrode to ferromagnetic 
workpieces. 
These and other objects, aspects, features and advantages of the present 
invention will become more fully apparent upon careful consideration of 
the following Detailed Description of the Invention and the accompanying 
Drawings, which may be disproportionate for ease of understanding, wherein 
like structure and steps are referenced generally by corresponding 
numerals and indicators.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1a is a system 10 for remotely controlling one or more operational 
parameters of an engine-driven welder having a welding cable and an 
electrode holder for supplying welding current to a workpiece W, and one 
or more operation controls for controlling corresponding operational 
parameters thereof. The system 10 remotely controls one or more 
operational parameters otherwise controllable locally from a control panel 
of the welder, including remotely enabling and disabling the welder, 
remotely choking the engine and controlling the idle thereof, remotely 
controlling coarse and fine current adjustment, and remotely reversing 
current polarity, among other operational parameters of the welder. 
In FIG. 1a, the engine-driven welder portion of the system 10 comprises 
generally a combustion engine 20 rotatably coupled to a generator 22 
having a rectifier 24 at its output for supplying welding current through 
a first cable portion 32 coupled to the workpiece W, and a second cable 
portion 34 coupled to an electrode holder 36, which includes an electrode, 
or weld stick, or stinger 37. The engine-driven welder includes a control 
panel 40 with operation controls for controlling operational parameters 
thereof locally as is known generally. The operation controls include, for 
example, a start switch, a run switch, a choke switch, a variable coarse 
current increase and decrease control 25, and a variable fine current 
increase and decrease control 27. The operation controls may be electrical 
contacts or solid state switching devices or other controls. Most ignition 
systems, for example, include generally a start switch and a run switch, 
wherein the start and run switches may be electrical contacts or solid 
state switches. The coarse current control is often a multi-tapped 
transformer, and the fine current control is usually a variable rheostat. 
FIG. 1b is a static welder system 11, which is similar in most respects to 
the engine-driven welder system 10 of FIG. 1a. except that the combustion 
engine 20 and generator 22 are replaced by an electrical converter 26 that 
converts an alternating current supply line input to an appropriate 
welding current supplied through a first cable portion 32 coupled to the 
workpiece W, and a second cable portion 34 coupled to an electrode holder 
36 having an electrode 37. The static welder also includes a control panel 
40 with operation controls for controlling operational parameters thereof 
locally similar to the controls on the engine-driven welder with the 
exception of the choke and possibly some other operation controls. The 
static welder system 11 also includes generally coarse and fine current 
controls, among other controls. 
The welder systems of FIGS. 1a and 1b further comprise generally a remote 
device 50 having one or more operational parameter signal circuits 
electrically coupleable between the workpiece W and the electrode holder 
36 for selectively producing unique operational signals on the welding 
cable, a signal sense circuit 60 for detecting the operational signals 
produced on the welding cable and for producing correspondingly unique 
operational sense signals in response thereto, and an operational control 
circuit 70, which may control drivers or relays 72 coupled to and 
actuating corresponding operation controls of the welder in response to 
the unique operational sense signals, thereby remotely controlling the 
operational parameters of the welder. 
FIGS. 2a and 2b illustrate a hand held battery powered pendant 80 for 
housing the one or more operational parameter signal circuits of the 
remote device 50 for selectively producing the one or more corresponding 
operational signals on the welding cable when electrically coupled between 
the workpiece W and the electrode holder 36. The pendent 80 has exposedly 
mounted thereon a first electrode 51 of the remote device 50 coupleable to 
the workpiece W and one or more second electrodes 52 of the remote device, 
only one of which is shown in FIGS. 2a and 2b, corresponding to the one or 
more operational parameter signal circuits, which are coupleable to the 
electrode holder 36 for generating corresponding operational signals on 
the welding cable. The pendent 80 includes a battery storage bay 81 for 
mounting and electrically coupling one or more batteries B to the 
operational parameter signal circuits of the remote device 50 also housed 
therein. The batteries B are required to power the remote device 50 to 
produce operational signals on the weld cable during some phases of 
operation as discussed further below. 
In one embodiment, the first electrode 51 is preferably disposed on an end 
82 of the pendent 80 where it is more readily electrically engageable with 
the workpiece W by an operator wielding the pendant 80. The one or more 
second electrodes 52 are disposed preferably on an upper surface 84 of the 
pendant 80 where they are readily and accessibly contactable by the 
electrode holder 36, including the electrode 37 thereof, to remotely 
control corresponding operational parameters of the welder as discussed 
further below. The first and second electrodes 51 and 52 of the remote 
device 50 include preferably pointed tips to facilitate electrically 
contacting the workpiece W and the electrode holder 36, despite the 
tendency for the formation of oxides on the electrodes 51 and 52, and on 
the electrode 37 of the electrode holder 36, and on the workpiece W. 
In another embodiment, the first electrode 51 is or includes a magnetic 
portion 53 disposed on a lower surface 86 of the pendant 80, wherein the 
magnetic portion 53 is magnetically and electrically coupleable to 
ferromagnetic workpieces. The pendent 80 may thus be adhered magnetically 
to the workpiece about a surface thereof by the operator during use. 
According to this aspect of the invention, the pendant 80 may be 
repositioned and remain adhered and electrically coupled to the workpiece 
when not in use, thereby reducing the possibility of misplacement thereof 
and eliminating the necessity of having to pocket or otherwise secure the 
pendant 80 between uses, which is a particularly convenient feature of the 
invention. 
FIG. 3 illustrates schematically a remote device 50 having the first 
electrode 51 and a plurality of second electrodes 52, 54, 55, 56, 57, and 
58, corresponding to a plurality of remotely controllable operational 
parameters of the welder, coupled to operational parameter signal circuits 
90 that produce corresponding operational signals on the welding cable 
when electrically coupled between the workpiece W and the electrode holder 
36. The operational parameter signal circuits 90 include, for example, 
among others a start signal circuit, a choke signal circuit, coarse 
current increase and decrease circuits, and fine current increase and 
decrease circuits for producing on the welding cable unique start, choke, 
coarse increase and decrease, and fine increase and decrease signals, 
respectively, depending on the particular type of welder. 
FIGS. 4a and 4b illustrate an exemplary operational parameter signal 
circuit of the remote device 50 for producing an operational signal on the 
welding cable when electrically coupled between the workpiece W and the 
electrode holder 36. The circuit includes a constant current source formed 
generally by op-amp OA1, transistor Q1, resistors R6 and R7, and capacitor 
C3. The output of the constant current source, and more particularly the 
collector of transistor Q1, is coupled to a corresponding one of the 
second electrodes 52 and 53-58, which is selectively coupleable to the 
electrode holder 36 to produce an operational signal on the welding cable. 
In the exemplary embodiment, diode D1 is disposed between the collector of 
Q1 and the electrode. 
The amplitude of the operational signal produced by the exemplary constant 
current source circuit is dependent on the values of resistor R1, R2, R3, 
R7. R8, R9 and R10. In embodiments that control more than one operational 
parameter of the welder, there is a corresponding number of constant 
current source circuits electrically coupled in parallel in the remote 
device 50, wherein the collector of the transistor of each constant 
current source circuit is coupled to a corresponding first electrode, 
which is selectively contactable by the electrode holder 36 in the hands 
of a welding operator to produce the desired operational signal on the 
welding cable. The current amplitude corresponding to the operational 
signals produced on the welding cable is unique for each remotely 
controlled operational parameter of the welder, as discussed further 
below, by appropriately selecting different resistive values R1, R2, R7 
and R8 for each of the constant current source circuits. 
FIGS. 4a and 4b illustrate the operational parameter signal circuit powered 
by a battery BAT1 coupled between the input pin 5 of the op-amp OA1 and 
the first electrode 51. The battery BAT1 also supplies power to the 
collector of the transistor Q1. The battery BAT1 is required to power the 
remote device 50 before starting the welder. After the welder is powered, 
however a DC voltage supplied by the welder is available on the welding 
cable between the workpiece W and the electrode holder 36, which may be as 
high as 85 volts or more on some welders. The DC voltage from the welder 
is thus available to power the operational parameter signal instead of the 
battery BAT1 when the welder is powered and the remote device 50 is 
electrically coupled between the workpiece W and the electrode holder 36. 
The remote device 50 of the exemplary embodiment requires at least 
approximately 4.8 volts to operate, although other embodiments may be 
configured to operate on less voltage. 
The remote device 50 also includes a switch SW1 for reversing the power 
supply polarity to the operational parameter signal circuit, and more 
particularly to the constant current source thereof. The power supply 
polarity reversal is required when the polarity of the welder is reversed 
at the control panel thereof as is desired for some welding applications. 
FIGS. 4a and 4b illustrate a timer circuit coupled between the op-amp OA1 
and the first electrode 51 including a 555 timer U1 having its output pin 
3 coupled to the input pin 5 of the op-amp OA1 by transistor Q3 to 
intermittently drive the constant current source, thereby producing an 
intermittent operational signal on the welding cable. In one embodiment, 
the timer circuit is configured to produce an ON/OFF pulse with a 20 
percent duty cycle, which in one configuration is ON for 100 milliseconds 
and is OFF for 400 milliseconds. The duty cycle of the 555 timer U1 is 
configurable by appropriate selection of resistors R13-R15, R18, R19 and 
C10. Other duty cycles may be used alternatively. The timer circuit is 
powered by a regulated voltage V+REG, as known generally, which is powered 
by either the battery or the DC voltage available on the welding cable. 
The intermittent operational signals generated by the constant current 
source reduce battery power consumption, which is particularly desirable 
when the remote device 50 is used to remotely start the welder and to 
remotely control other operational parameters thereof before the welder is 
running. 
In embodiments having a plurality of constant current source circuits 
electrically coupled in parallel for controlling a corresponding plurality 
of operational parameters of the welder, as discussed above, a single 
timer circuit may modulate one or more of the constant current source 
circuits through a common driver transistor Q3. Thus, the remote device 50 
includes generally a plurality of constant current source circuits 
arranged in parallel, and coupled to a corresponding second electrode for 
producing a corresponding plurality of unique operational signals on the 
welding cable when electrically coupled between the workpiece W and the 
electrode holder 36. The constant current source circuits may be driven by 
an intermittent drive signal from a timer circuit, which is desirable for 
reducing power consumption when remotely controlling operational 
parameters of the welder under battery power. 
In the exemplary embodiment generally, the start signal circuit is a 
constant current source circuit, and the start signal produced on the 
welding cable is preferably a relatively low amplitude intermittent 
operational signal of approximately 0.5 amps and having a 20 percent duty 
cycle thereby minimizing battery power consumption since the remote device 
50 operates on battery power to produce the start signal. Other 
operational signals produced by the remote device on the welding cable 
prior to starting the welder, for example the choke signal, are also 
preferably low amplitude intermittent signals to reduce battery power 
consumption. The higher amplitude current signals are preferably reserved 
for remotely controlling operational parameters while the welder is 
running, for example the coarse and fine current adjustments, since the 
energized welding cable has a low DC voltage thereon, which may be used by 
the remote device 50 for producing the higher amplitude signals. 
FIG. 4a also illustrates an indicator circuit with a visual display for 
indicating when the welder is providing a DC voltage on the welding cable, 
and thus that the welder is powered. In the case of an engine-driven 
welder, the visual display is indicative that the engine is running. The 
indicator circuit includes a current limiting resister R20, and a zener 
diode D6 in series with a lamp LED1, which is preferably mounted in a 
visually conspicuous location on the pendant 80. 
FIGS. 1a and 1b illustrate a signal sense circuit 60 for detecting the 
operational signals produced on the welding cable, and for producing 
corresponding operational sense signals in response thereto. The signal 
sense circuit 60 is disposed generally along the welding cable, wherein 
the welding cable includes the welding cable portions 32 and 34 and any 
other conductor in the rectifier 24 and generator 22 or electrical 
converter 26 supplying current thereto, and through which the operational 
signals are communicated and detectable by the signal sense circuit 60. 
The signal sense circuit 60 may include a differential amplifier coupled 
across a low resistance resistor, for example a 5 ohm resistor, disposed 
in series along the welding cable, wherein the resistor is protected by 
two diodes arranged in parallel with the resistor, but with polarities 
reversed. 
In a preferred embodiment, the signal sense circuit 60 is a current sensor 
circuit, for example a commercially available current transformer. 
According to this embodiment, the remote circuit 50 produces preferably an 
alternating carrier wave for the operational signals. The alternating 
carrier wave distinguishes the operational signals from noise on the 
welding cable thereby facilitating detection of the operational signals by 
the current transformer. FIG. 4a illustrates, more particularly, an 
oscillator circuit coupled to the input pin 5 of the constant current 
source op-amp OA1, whereby the timer circuit modulates the AC signal from 
the oscillator circuit at the input pin 5 of the constant current source. 
The timer circuit is not an essential feature, although it remarkably 
increases the longevity of the batteries. 
The oscillator circuit includes generally an op-amp U2, wherein the 
oscillation frequency is dependant upon the resistors R1-R3, R9, R10 and 
the capacitor C6 coupled thereto. In the exemplary embodiment, the 
frequency is preferably not less than approximately 900 Hertz, but may be 
more or less. Frequencies at this exemplary level, and higher, increase 
the signal strength from the current transformer sense circuit 60, and 
facilitate improved filtering thereof by an instrumentation circuit 
thereby providing less noisy signals to the controller 70 discussed 
further below. In embodiments having a plurality of constant current 
source circuits electrically coupled in parallel for controlling a 
corresponding plurality of operational parameters of the welder, as 
discussed above, a single oscillator circuit may provide the AC carrier 
signal to the plurality of constant current source circuits. 
FIGS. 5a and 5b illustrate an exemplary instrumentation circuit coupled to 
the output of a current transformer signal sense circuit 60. In FIG. 5a, 
the instrumentation circuit includes a differential amplifier circuit 
formed by op-amps A11-A13. The gain of the amplifiers A11, A12 and A13 is 
set by feedback resistors R33-R35, R43, R44, R45 and R47 and corresponding 
parallel capacitors C4, C6 and C7. The input to the instrumentation 
amplifier is clamped by zener diode D5, and a high wattage resistor R39 
dissipates excessive power applied thereto. In embodiments that include 
the alternative resistive signal sense circuit discussed above, the 
instrumentation circuit portion of FIG. 5a may not be required. 
FIG. 5a illustrates further a signal stabilization and wave shaping circuit 
to stabilize and shape the operational sense signal generated by the sense 
signal circuit 60 in response to the operational signal produced by the 
remote device 50 on the welding cable. The signal stabilization and wave 
shaping circuit includes op-amps A14 and A23, rectifying diodes D21 and 
D31, resistors R31, R32 and R40-R42, and capacitor C5 for rectifying any 
negative component of the signal from op-amp A13. The signal stabilization 
and wave shaping circuit may alternatively be coupled to the output of the 
alternative resistive signal sense circuit 60 discussed above. 
FIG. 5b also illustrates an operational signal sense disable circuit 
coupled generally to the output of the signal sense circuit 60, and in the 
exemplary embodiment to the output of the signal stabilization and wave 
shaping circuit at capacitor C5. A transistor Q7 pulls the capacitor C5 to 
ground in response to an input signal thereto indicating that the welder 
is providing power either for welding or to some other load coupled to an 
accessory AC outlet at the control panel of the welder. 
In engine-driven welders, the input signal driving transistor Q7 is 
supplied, for example, from an idle module or an excitation rectifier of 
the welder. The signal is rectified by diode D6 and filtered by capacitors 
C31, C32 and resistor R48, and is isolated optically from the transistor 
Q7 by switch U6. When transistor Q7 is turned ON, by the presence of the 
input signal from the idle module or the excitation rectifier of the 
welder, the operational sense signal at the output of capacitor C5 is 
grounded, thereby blanking any input to the controller, and more 
particularly the comparator circuits of FIG. 6a discussed further below, 
to disable the remote control of the welder. In static welders the input 
signal driving the transistor Q7 is supplied from a load sensor, like a 
current transformer, in the electrical converter 26. 
The operational sense signals generated by the signal sense circuit 60 are 
provided generally to a bank of comparator circuits of FIG. 6a. In the 
exemplary embodiment, the operational sense signals are supplied to the 
instrumentation circuit and the signal stabilization and wave shaping 
circuit, which in turn supply the operational sense signal to the 
comparator circuits of FIG. 6a. There are eight comparator circuits U1 and 
U2. Six of the comparator circuits correspond to remotely controllable 
operational parameters of the welder, which may for example be the 
operational parameters identified on the remote device in FIG. 3. There 
may be more or less, however, corresponding to the desired number of 
operational parameters controlled remotely. The six comparator circuits 
produce an output signal when the amplitude of the operational sense 
signal produced by the signal sense circuit 60 input thereto is at a 
threshold level determined by the resistive divider network formed by 
resistors R4-R7 and R16-R19 and R21. In the exemplary embodiment, for 
example, the threshold voltage for the comparator circuits differs by 0.5 
volts and ranges between 0.5 volts and 4 volts, and the six comparator 
circuits corresponding to the operational sense signals have threshold 
voltages between 0.5 and 3.0 volts. 
In the exemplary embodiment, the comparator having the lowest threshold of 
0.5 volts and the comparator having the highest threshold of 4.0 volts 
define upper and lower limits on the range of signals interpreted by the 
microcontroller U4, wherein signals outside these range limits are 
disregarded as noise, and may be indicative that the welder is supplying 
power to a load, either via the welding cable or accessory AC outlets 
thereon. 
FIG. 6b illustrates the comparator circuit outputs coupled to a 
microprocessor based controller U4. The microcontroller U4 is programmed 
to determine which operational signal was produced by the remote device 50 
on the welding cable based on the combination of comparator output signals 
produced in response to the operational sense signal input thereto. For 
example, a 1.5 volt signal generated by the sense signal circuit 60 in 
response to an operational signal produced on the welding cable will 
produce outputs from the three comparators circuits having thresholds of 
0.5 volts, 1.0 volts and 1.5 volts. The microcontroller U4 is programmed 
to interpret the outputs from the comparator circuits as corresponding to 
a particular operational signal, and responsively actuates or de-actuates 
one or more corresponding operation controls at the control panel of the 
welder as discussed further below. Thus by producing unique operational 
signals on the welding cable with the remote device 50, which in the 
exemplary embodiment are defined by unique current amplitudes, the remote 
device 50 can transmit operational signals from the remote weld site along 
the welding cable back to the microcontroller U4, which interprets the 
operational signals and performs some control function at the control 
panel of the welder in response thereto as discussed further below. 
FIG. 7a illustrates outputs of the microcontroller U4 coupleable to several 
exemplary operation controls of an engine-driven welder control panel 
including more particularly an idle operation switch, a choke operation 
switch, a starter operation switch and a run operation switch. Generally, 
the outputs on lines 2, 3, 6 and 8 of the microcontroller drive 
corresponding FETs Q6, Q10, Q11 and Q3, which energize corresponding 
relays CR3, CR2, CR1 and CR4, respectively, in response to outputs from 
the microcontroller U4. The relays CR3, CR2, CR1 and CR4 are tied to the 
existing run, starter, choke, and idle operation switches in the control 
panel of the engine-drive welder. 
Engine-driven welders include generally a start switch and a run switch for 
starting and running the welder. The run switch is usually actuated "on" 
initially by a switch at the control panel of the welder. To start the 
engine-driven welder, the start signal circuit in the remote device 50 is 
electrically coupled between the workpiece W and the electrode holder 36 
to produce a start signal on the welding cable. This is performed by 
touching the electrode holder 36 onto the run/stop electrode 54 
illustrated in FIG. 3 and contacting the first electrode 51 to the 
workpiece W. The sensor circuit 60 detects the start signal and produces a 
start sense signal in response thereto, which is transmitted to the 
controller 70, or microcontroller U4. If the welder is not running when 
the microcontroller U4 receives the start signal sense signal from the 
signal sensor 60, the microcontroller U4 energizes the starter relay to 
actuate the start switch of the welder. The microcontroller U4 determines 
whether the welder is running by monitoring the ignition coil frequency as 
discussed further below. After the welder starts and is running, the 
Microcontroller U4 de-energizes the starter relay, thereby de-actuating 
the start switch. 
If the engine-driven welder is already running when the microcontroller U4 
receives the start sense signal, the microcontroller will at least 
momentarily de-energize the run relay in response thereto, thereby 
stopping the engine-driven welder. The starting and stopping of the welder 
may be controlled remotely by electrically coupling the start signal 
circuit between the workpiece W and the electrode holder 36. The first 
start signal produced by the remote device on the welding cable starts the 
welder and a subsequent start signal stops the welder. 
FIG. 7a illustrates an ignition coil of the engine-driven welder coupled to 
the microcontroller, which monitors the frequency thereof to determine 
whether the engine-driven welder, and more particularly the engine 20 
thereof, is running or is merely being cranked by the starter motor 
thereof. The ignition coil frequency signal is filtered by resistor R8 and 
capacitor C9, and is optically coupled by U7 to the trigger input of a 555 
timer circuit U5, which provides an input to pin 11 of the microcontroller 
U4. A relatively low frequency signal, approximately 8 Hertz in the 
exemplary embodiment, is indicative that the engine 20 is being cranked by 
the starter motor but is not yet running, whereas a higher frequency 
signal is indicative that the engine-driven welder is running. The 
ignition coil frequency signal is used by the microcontroller U4 to 
determine when the engine is running and when to disable the starter 
switch when the engine-driven welder is started remotely as discussed 
above. In the exemplary embodiment, the microcontroller U4 is programmed 
to disable the starter switch when the ignition coil frequency signal is 
approximately 16 Hertz. 
In engine-driven welder applications, the microcontroller U4 is preferably 
programmed to increase the idle of the engine-driven welder by energizing 
relay CR4 on the output 8 thereof prior to starting the engine so that the 
engine starts at high idle. The engine-driven welder includes a load 
sensor circuit that increases or decreases the idle based on the 
electrical load drawn through the welding cable or by an auxiliary 
electrical outlet located on the front panel, as is known. The load sensor 
circuit will subsequently reduce the engine idle after starting in the 
absence of a load. 
Engine-driven welders may also include an audio or visual indicator that is 
momentarily energized prior to starting the engine as a safety feature. 
FIG. 5c illustrates, more particularly, the microcontroller U4 output 7 
coupled to a FET Q9. The controller U4 is programmed to temporarily 
energize a horn or other indicator driven by the FET Q9 prior to starting 
the welder in response to a start signal from the remote device. 
The microcontroller U4 may also be programmed to temporarily energize the 
choke relay CR1 to choke the engine-driven welder prior to starting, or 
while cranking the engine if the engine does not start after a 
predetermined time period upon actuating the starter switch. In the 
exemplary embodiment of FIG. 3, the choke is also remotely controllable by 
the remote device 50, which may be desired prior to starting the 
engine-driven welder. To choke the engine-driven welder, a choke signal 
circuit in the remote device 50 is electrically coupled between the 
workpiece W and the electrode holder 36 to produce a choke signal on the 
welding cable. The sensor circuit 60 detects the choke signal and produces 
a choke sense signal in response thereto, which is transmitted to the 
controller 70, or microcontroller U4 in FIG. 6b. 
FIG. 7a also illustrates an output line 9 of the microcontroller U4 coupled 
to FET Q1 for driving lamp LED1, which may be programmed for diagnostic 
purposes, for example to indicate the presence of noisy signals from a 
current sensor circuit 60 which are outside the upper range limit of the 
comparator circuits of FIG. 6a during calibration of the system. 
The microcontroller U4 may more generally be coupled to alternative or 
additional operation controls as discussed hereinabove, including coarse 
and fine current controls, a polarity reversal switch, an AC/DC select 
switch, and a wire feed switch, among others, on the control panel of the 
welder. 
In the case of the coarse and fine current adjustment controls, the 
microcontroller U4 includes corresponding fine current increase and 
decrease outputs and coarse current increase and decrease outputs, which 
drive corresponding stepper motors or solenoids or other known control 
devices that increase and decrease the coarse and fine currents. For 
example, each time the electrode holder 36 is touched onto the electrode 
57 of the remote device 50 corresponding to the fine current increase, as 
shown in FIG. 3, a fine increase signal is produced on the welding cable 
and is detected by the signal sensor 60, which in turn generates a 
corresponding current increase sense signal that is transmitted to the 
controller 70. The controller 70 then responsively produces a control 
signal that operates the fine current increase control, usually a stepper 
motor or solenoid controlled variable rheostat, to increase the fine 
current some predetermined incremental amount programmed into the 
controller. The other current controls operate similarly. The controller 
70 thus controls the operation controls on the control panel of the welder 
in response to corresponding operation signals produced on the welding 
cable by the remote device 50 thereby permitting remote control thereof. 
While the foregoing written description of the invention enables one of 
ordinary skill in the art to make and use what is at present considered to 
be the best mode of the invention, it will be appreciated and understood 
by those of ordinary skill the existence of variations, combinations, 
modifications and equivalents within the spirit and scope of the specific 
exemplary embodiments disclosed herein. The microcontroller may for 
example be replaced with analog and or other digital circuity. The present 
invention is therefore to be limited not by the specific exemplary 
embodiments disclosed herein but by all embodiments within the scope of 
the appended claims.