Add foot switch to laminator

Thread Starter

geo86

Joined Apr 8, 2018
4
Hi,

I have a laminator GBC Catena 65 and it doesn't not have a foot pedal (foot switch) which is a bit annoying.
I have tried to find the schematic diagram online without success and the main board circuits are above my knowledge and understanding.

So what I need to do is to add an ordinary foot switch (pedal) that will allow me to start and stop the laminator by foot.

I was wondering if someone can provide some guidance by just looking at the attached pictures? Possibly not but just asking...

So the display and the keypad seems to be connected to the integrated circuit (which I believe is a microcontroller) then sends the signal to the relay next to the big black capacitor. So when I press the button RUN the relay will be powered and contacts closed. When I press the button STOP, the power to the relay is cut off, contacts open, motor stops.

However, I have used a bridge (a wire) to power the relay without pressing RUN, the contacts closed but the motor won't run. I believe there is a second circuit that needs to be powered/closed or that is not the right spot to put the foot switch but I really have no clue.

If you need certain information or more pictures please let me know.

Thank you on advance.
 

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-live wire-

Joined Dec 22, 2017
959
BE CAREFUL! There could be capacitors charged to lethal voltages. They can hold a charge for a very long time, even when disconnected. If you do not have a decent knowledge of electricity and electrical safety, please do not open it up and try to modify it. If you plan to make any sort of modifications, please make sure everything is unplugged, too.

So from my understanding, this is how it works: you press a push-button, and it spins a motor while you are pressing it, but then stops when you let go? If that is the case, you can just solder some extension wires to it so that you can press it with your foot. You could maybe attach a piece of wood or plastic to make it more like a foot pedal. If you do not have access to a soldering iron, you can probably just take it out with pliers and then glue the wires in place.

Edit: Sorry, I did not read through what you said thoroughly enough. So you press the "go" button and it starts and when you press "stop" it stops the motor? Does it stop when you release the "stop" button or when you press it down? And could you hold down "go" or "stop" forever without any problems?

If so, then you just need a simple circuit that based on one input (an on/off button or switch) gives you one inverted output and one normal one. The inverted output goes to where the "stop" button previously was. The normal one goes to where the "go" button was. This way, it's like someone is always pressing "stop", until someone presses go and releases the "stop" button. This inversion can easily be done with a p-channel mosfet. Feel free to ask questions about how exactly something like this would work, and how you might wire it up.
 
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Reloadron

Joined Jan 15, 2015
7,523
A Google of "Foot Switches" should bring up a few dozen hits. I see a good selection on Amazon. Part of this involves looking at the existing switch and taking note of the switch ratings. Then select a switch with the same or greater ratings.

So when I press the button RUN the relay will be powered and contacts closed. When I press the button STOP, the power to the relay is cut off, contacts open, motor stops.
Now if there are two buttons, Stop & Start that leads me to believe there is a latching type circuit used, a momentary push of On starts things and they run till a momentary push of Off stops things. The whole idea is knowing exactly what you have and how it works.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
28,702
The way I read it it has a HMI & keypad, one of which is the Run/Start P.B. This makes it rather tricky to divert or parallel the start signal if this is so.
It would need some reverse engineering of the keypad interface and detect where it ended up and also the format of the Keypad, i.e. simple 4x4 matrix or intelligent decode IC etc.
Max.
 

Thread Starter

geo86

Joined Apr 8, 2018
4
Thank you, I am aware of the electrical hazard, I never work on live circuits and I am aware of the risk posed by the capacitors even with power switched off.

The whole circuit is pretty low voltage, I think 16V and 32V except two halogen heaters inside the rollers that seems to be powered through the triac and that seems to be high voltage (possibly 240V, I didn't chase the circuits).

The keypad has two separate buttons, RUN and STOP, see attached. I do not need to press&hold the RUN button in order to have the motor running. I just press once RUN and it's running, if I need to stop, I press once the STOP. So there is no option to add a parallel switch because in the best case scenario the foot pedal will only simulate the function of the RUN button without option to stop.

The CI is a PIC16F877A (http://www.microchip.com/wwwproducts/en/PIC16F877A).

My understanding is the keypad buttons signals are processed by the CI and diverted to the appropriate circuits. i.e. temperature, speed, direction etc.
But the PCB is double-sided and is really hard to chase and I don't quite understand how it works anyway.
 

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Thread Starter

geo86

Joined Apr 8, 2018
4
Now if there are two buttons, Stop & Start that leads me to believe there is a latching type circuit used, a momentary push of On starts things and they run till a momentary push of Off stops things. The whole idea is knowing exactly what you have and how it works.
Ron
To me it seems to be a latching type circuit, please see my reply above for further info. Many thanks
 

MaxHeadRoom

Joined Jul 18, 2013
28,702
I would guess then it could be a matrix set up for the keypad.
It appears the keypad/display could be proprietary for the OEM.
Not going to be that simple, I suspect.
Max.
 

-live wire-

Joined Dec 22, 2017
959
You can try a brute force approach. Just step down the voltage using a linear regulator or something to get the voltage the relay needs. Interrupt the traces to it (or just completely remove the coil part from the PCB). Put the pedal in series, and it should work as long as the relay directly controls the motor.
 

Reloadron

Joined Jan 15, 2015
7,523
I would guess then it could be a matrix set up for the keypad.
It appears the keypad/display could be proprietary for the OEM.
Not going to be that simple, I suspect.
Max.
I tend to have to agree with Max on this. In your first images posted there is a large chip below the pizeo buzzer with a white label which looks to be a propitiatory chip, likely including a micro controller. The keypad looks to be a 3 X 4 matrix with 2 keys left out. The matrix is likely read by the propitiatory controller which then outputs logic commands to the board. Without knowing exactly what is doing what I really do not see a simple solution or work around. Not saying it can't be done, only saying I do not see an easy solution. There may be a way to hack into the keypad matrix but I won't suggest doing that. Really bad things can happen and or go wrong.

Ron
 

Thread Starter

geo86

Joined Apr 8, 2018
4
I tend to have to agree with Max on this. In your first images posted there is a large chip below the pizeo buzzer with a white label which looks to be a propitiatory chip, likely including a micro controller. The keypad looks to be a 3 X 4 matrix with 2 keys left out. The matrix is likely read by the propitiatory controller which then outputs logic commands to the board. Without knowing exactly what is doing what I really do not see a simple solution or work around. Not saying it can't be done, only saying I do not see an easy solution. There may be a way to hack into the keypad matrix but I won't suggest doing that. Really bad things can happen and or go wrong.

Ron
The chip is a PIC16F877A (http://www.microchip.com/wwwproducts/en/PIC16F877A), I have removed the white label, and it is a microcontroller.

I have no intention to hack the keypad or the PCB so if the solution is more complex than soldering two wires, I'll give it up, it's not worth the hassle.

I'll open the machine again tonight and I'll come back with some more info, schematic etc.
 

MaxHeadRoom

Joined Jul 18, 2013
28,702
A non-invasive Rube Goldberg fix might be a compact pair of solenoids mounted on a frame over each button, you would need two foot pedal switches for On-OFF.
Danfoss make miniature solenoids with their Comatrol line.
Most solenoids pull in to the coil so a little modification may have to be done, including bringing the actuator through the rear of the valve body, this way you would also retain the manual push.
Just an idea to explore if wishing to be non invasive as possible.;)
Max.
 
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