PCB Boards -- Simple Machinery

[JohnerH]

Morning All,

Quick, silly question... Given the simplicity (or at least it used to be) of the mechanical elements in things like jointers and band saws for instance, why is there a need for PCBs in them?

Reason for my ask is that I am troubleshooting a jointer at the moment and will probably have to send the PCB out to get checked, but since this question occuered to me, I thought I'd ask

(not to mentioned in a few month time I'll be opening up all sorts of Wadkin kit which I'm sure won't have any PCBs)

J

 

[Fitzroy]

My relatively uneducated thought would be that PCBs are now so cheap they represent an easy/cheap way to add some protection/control to any electronic device. Traditional control and protection systems are likely more expensive, although more user maintainable.

Your Wadkin will still have a contactor in the starter somewhere with a latching relay, and some overload/thermal protection. It'll be built with electronics of the time so no PCBs and at a scale that is much easier to understand.

edit: Your, not You're

 

[Sideways]

The older, trade and above machines I tinker with don't need PCB's.
I can think of only a few reasons.
1. Anything with an LED or LCD display in it for speed or distance, or LEDs.
2. Machines that use brushed motors or modern brushless motors. In that case it will be for the speed control. Both these technologies are cheaper than an AC induction motor with a VFD.
3. A machine with a number of safety switches might have these on plug in leads and a simple PCB to in the middle just because the components will be cheap and assembly will be easy. A proper dust sealed enclosure with cable glands and screw terminals would be far superior but much more expensive to pay a factory worker to hand wire it up.
4. Much more unusual but you could encounter a DC brake or a low power VFD implemented as a PCB for inclusion inside something else rather than a standard module.

 

[Spectric]

Quick, silly question... Given the simplicity (or at least it used to be) of the mechanical elements in things like jointers and band saws for instance, why is there a need for PCBs in them?

Same reason why they are now in almost everything from your car to the hoover and everything in between. I would say the word control is key, but at the same time there are a lot of instances where the excuse will be " because we can" . Looking at machinery, people have been using heavy machinery far longer than we have had even basic analogue electronics let alone digital and they were producing items to close tolerances and measuring with mechanical micrometers with no digital readout. Here we can divide the reasons, home / hobby workshop then really very little need to add complexity to our machines apart from maybe DRO's or bolt ons, in industry we have electronics controlling most machines involved in production and is the norm. Electronics also offers a cost effective solution to brushless cordless tools in areas of commutation, battery monitoring and torque control which are not found on your machinery with Ac motors unless you are using something like a digital phase convertor to run a three phase machine from a single phase supply.

A downside of many modern PCB's is when they use a microcontroller, think of it as a black box and now when things go wrong it is much harder to undertake fault finding and more expensive when the PCB has to be replaced. If you want some idea of what lurks within a microcontroller within a brushless Dc motor control system, ie cordless drill or E bike then here is a overview of the algorithm that will be implemented in software.

 

[JohnerH]

Same reason why they are now in almost everything from your car to the hoover and everything in between. I would say the word control is key, but at the same time there are a lot of instances where the excuse will be " because we can" . Looking at machinery, people have been using heavy machinery far longer than we have had even basic analogue electronics let alone digital and they were producing items to close tolerances and measuring with mechanical micrometers with no digital readout. Here we can divide the reasons, home / hobby workshop then really very little need to add complexity to our machines apart from maybe DRO's or bolt ons, in industry we have electronics controlling most machines involved in production and is the norm. Electronics also offers a cost effective solution to brushless cordless tools in areas of commutation, battery monitoring and torque control which are not found on your machinery with Ac motors unless you are using something like a digital phase convertor to run a three phase machine from a single phase supply.

A downside of many modern PCB's is when they use a microcontroller, think of it as a black box and now when things go wrong it is much harder to undertake fault finding and more expensive when the PCB has to be replaced. If you want some idea of what lurks within a microcontroller within a brushless Dc motor control system, ie cordless drill or E bike then here is a overview of the algorithm that will be implemented in software.

View attachment 184984

Fanstatic explanation thank you @Spectric, only wish I knew enough to ascertain whether the fault is with the PCB.

Sending this to Record Power, I might as well buy a new one.

Anyway I shall plod, learn as ascertain with time

Thank you again.

 

[Spectric]

@JohnerH What machine are you having issues with ?

 

[JohnerH]

Record Power - RSPT 260

 

[nickds1]

Same reason why they are now in almost everything from your car to the hoover and everything in between. I would say the word control is key, but at the same time there are a lot of instances where the excuse will be " because we can" . Looking at machinery, people have been using heavy machinery far longer than we have had even basic analogue electronics let alone digital and they were producing items to close tolerances and measuring with mechanical micrometers with no digital readout. Here we can divide the reasons, home / hobby workshop then really very little need to add complexity to our machines apart from maybe DRO's or bolt ons, in industry we have electronics controlling most machines involved in production and is the norm. Electronics also offers a cost effective solution to brushless cordless tools in areas of commutation, battery monitoring and torque control which are not found on your machinery with Ac motors unless you are using something like a digital phase convertor to run a three phase machine from a single phase supply.

A downside of many modern PCB's is when they use a microcontroller, think of it as a black box and now when things go wrong it is much harder to undertake fault finding and more expensive when the PCB has to be replaced. If you want some idea of what lurks within a microcontroller within a brushless Dc motor control system, ie cordless drill or E bike then here is a overview of the algorithm that will be implemented in software.

View attachment 184984

Being fair, that's a 3-phase controller and unlikely to be used in a cordless drill. Single phase is considerably simpler, though it may include PID algorithms for set point hysteresis reduction under load etc.

 

[imageel]

@JohnerH - It would greatly aid those offering help to you if you gave some details as to what fault you are attempting to fix...

 

[JohnerH]

@JohnerH - It would greatly aid those offering help to you if you gave some details as to what fault you are attempting to fix...

This...

And I know it's not the capacitor...

 

[Spectric]

that's a 3-phase controller and unlikely to be used in a cordless drill

When using brushless Dc motors there is no point in using a single phase motor, having three phases allows for far better torque and the basic concept of using FOC is to ensure that the magnetic fields are produced at the optimum angles. Also remember a single phase Ac motor will require some form of starting mechanism be it a capacitor or another winding, with electronic commutation the three rotating magnetic fields are produced using space vector modulation (SVM).

 

[Spectric]

Record Power - RSPT 260

I have the Record PT107 which has no PC boards and the wiring diagram for your machine is similar. Where is this PCB ?

It would greatly aid those offering help to you if you gave some details as to what fault you are attempting to fix...

That would help now we know what the machine is, also @JohnerH you video is not working. I find that I need to keep the safety switchs clean on my PT107 otherwise when you shut the door they can fail to operate and this prevents the machine from operating.

 

[Sideways]

Hi @JohnerH

I've looked at Record Power's youtube video about the RSPT260 - oldish thing presented by Alan Holtham - and it looks very generic.
They don't say but your video clip suggests it is a single phase induction motor. Permanent split capacitor type. That doesn't need a PCB.
From the video, there is a safety switch on the front of the machine that is there to prevent it running if the tables are removed for thicknessing and the dust chute / blade guard isn't in position. I would not be at all surprised if there was a simple pcb to connect this interlock to the switches inside the box on the front. A pcb for that job would be very simple, just an alternative to joining everything up with loose wires.
The RP video says that the machine has a mechanical, not electrical, brake. This may mean some friction material, springs, and a disc or drum to slow the rotor down. There might then need an electrical solenoid to disconnect the brake while the motor is running. That would be worth investigating.
You say you know that the problem isn't the capacitor. Can you tell us how please ?
Even without a capacitor, a motor should still spin (but not at full power) if you spin it by hand to get it started.

Any chance of a photo of the PCB wherever it is ?

 

[JohnerH]

Apologies all,

Just read this, give me a couple of hours to get myself up and running and I'll get more pictures

Thank you for the help.

 

[JohnerH]

I have the Record PT107 which has no PC boards and the wiring diagram for your machine is similar. Where is this PCB ?

It's connected directly in several ways to the power switch.

I really need to write up the wiring diagram along with labelling the wires, all the wires are black which doesn't help matters.

That would help now we know what the machine is, also @JohnerH you video is not working.

Seem to fine, I can load it on different platforms... essentially it's just motor jittering.

I find that I need to keep the safety switchs clean on my PT107 otherwise when you shut the door they can fail to operate and this prevents the machine from operating.

I connected all the switches directly as to eliminate them as a fault point.

Hi @JohnerH

I've looked at Record Power's youtube video about the RSPT260 - oldish thing presented by Alan Holtham - and it looks very generic.
They don't say but your video clip suggests it is a single phase induction motor. Permanent split capacitor type. That doesn't need a PCB.

From the video, there is a safety switch on the front of the machine that is there to prevent it running if the tables are removed for thicknessing and the dust chute / blade guard isn't in position. I would not be at all surprised if there was a simple pcb to connect this interlock to the switches inside the box on the front. A pcb for that job would be very simple, just an alternative to joining everything up with loose wires.

Quite frankly, I had a feeling that would be the case. Quite temped just to wire everything manually.

The RP video says that the machine has a mechanical, not electrical, brake. This may mean some friction material, springs, and a disc or drum to slow the rotor down. There might then need an electrical solenoid to disconnect the brake while the motor is running. That would be worth investigating.

What would this look like?

You say you know that the problem isn't the capacitor. Can you tell us how please ?

Changed the capacitor and when I hooked it direct to the mains it ran smoothly and then when I switched the terminals on the capacitor the rotor direction changed, which told me the capacitor is doing it's job.

Even without a capacitor, a motor should still spin (but not at full power) if you spin it by hand to get it started.

Any chance of a photo of the PCB wherever it is ?

Attached...

Forgot to add,

When assessing the wires going into the motor, I found out that 3 of the wires (the 2 blacks and the blue) were Live!

The blue one less so/power... but nonetheless... surely that isn't right?

Let me know your thoughts.

 

[imageel]

Hi, It sounds like the electronic brake is permanently engaged.
I'd suspect that that PCB likely controls the brake mechanism, and it looks like the middle of 3 resistors in the 1st pic bottom right has burnt and is likely open circuit. It appears to be 22Ω - colour code indicates value and it's upside down so red-2 red-2 black-0-multiplier = 22 ohms and judging by the size of it 1/2w rated.
If you have a meter you could measure it and compare to the other 2 which are the same value and if open cct simply cut it out close to the brown resistor body and solder in a replacement across the remaining leads- loads of choices on ebay for little money. Or if you have a de-soldering tool remove the solder from the PCB wiring side and replace the device that way.
It maybe the replacement will blow if another fault persists, but worth a try
Good Luck !

 

[JohnerH]

Hi, It sounds like the electronic brake is permanently engaged.
I'd suspect that that PCB likely controls the brake mechanism, and it looks like the middle of 3 resistors in the 1st pic bottom right has burnt and is likely open circuit. It appears to be 22Ω - colour code indicates value and it's upside down so red-2 red-2 black-0-multiplier = 22 ohms and judging by the size of it 1/2w rated.
If you have a meter you could measure it and compare to the other 2 which are the same value and if open cct simply cut it out close to the brown resistor body and solder in a replacement across the remaining leads- loads of choices on ebay for little money. Or if you have a de-soldering tool remove the solder from the PCB wiring side and replace the device that way.
It maybe the replacement will blow if another fault persists, but worth a try
Good Luck !

Question is... is it worth having a PCB on here? Like... seriously...

I'm not going to sell nor do I plan to move this jointer to anyone else.

 

[imageel]

Oh you might also want to check the fuse too - albeit it's 13A and if it had blown I'd not expect to see much of the resistor left...

 

[imageel]

Agreed, if you can work out which leads control the brake and/or if the brake needs to be permanently energised to release then you could ignore the electrickery and disconnect the brake leads.
However I suspect the mechanism is spring loaded such that in the event of power loss the brake is auto applied as a safety feature, so you may have to physically disengage the brake permanently and live without it

 

[JohnerH]

Oh you might also want to check the fuse too - albeit it's 13A and if it had blown I'd not expect to see much of the resistor left...

Checked the fuse... all good...

Agreed, if you can work out which leads control the brake and/or if the brake needs to be permanently energised to release then you could ignore the electrickery and disconnect the brake leads.
However I suspect the mechanism is spring loaded such that in the event of power loss the brake is auto applied as a safety feature, so you may have to physically disengage the brake permanently and live without it

I don't think so, when I hooked up the motor directly to the mains (with the capacitor in) it ran smoothly.