Hawk / Active8 Reflow oven temperature regulation

[phonoplug]

I have a Hawk / Active8 conveyor reflow oven, not exactly sure of the model as it has no name plate or anything on it. Its 6 zone, 3 above and 3 below. Its meant to be 3 phase 415V, though I'm powering it from 240V no problem (thats another story) - apparently the same machine was available in single phase 240V and that's basically the conversion I've done.

I'm finding the temperature regulation a bit sketchy - it can be at the correct temperature one minute and when I look back at the PC next time its more than 20 degrees out. This seems to affect all zones including the reflow zone which looks as though it should be controlled more accurately than the others, going by the PC screen.

I've ruled out dodgy connections to the thermocouples for each zone and have now spent more time investigating the system as a whole. I have a couple of theories about it which I need to test out, but am waiting some components to allow this. Its a bit of a mission getting to the PCBs inside it because if the size and weight of the thing, so I really don't want to be trying out loads of different things if possible to fix it.

Has anyone else got one of these? Have you seen any similar problems, and are you still using it with the original PC it was supplied with? (that last question refers to a theory I have).

Oh, and do you know what model mine might be?! Its got a chain-male conveyor that's about 330mm wide and I think overall length is about 2 meters.

[Teuneman]

Does it look like the attached image?

I have an SMT IRC375 Model. Sounds like you've got one of the same range. There's a IRC250(230/440VAC), IRC300(440VAC), and IRC375(440VAC).I don't know if my PC is the original. I will try to find out but it probably is.
I usually don't start as soon as I see it is "running system stable" because it usually isn't, it still fluctuates with about 10-15 degrees. The oven is more or less ready in 30mins time, depending on the season. Does your temp go over or under? I've got a hood that goes over with fans and an extractor too.



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[phonoplug]

Aaaha yes, that looks very much like it though mine's cream coloured rather than blue. Otherwise it seems to have the same bits in the same places.

Its temperature seems to fluctuate both up and down, in all zones. I have now made some improvements to the control board (including re-writing the firmware) which I have tested on the bench. I think it should work significantly better now. Just need to put it back in the machine and fire it up for real.

I also noticed that the PCB design was not great. Mains potential tracks right next to optically isolated tracks at the same potential as the PC's serial port. Not good.

[phonoplug]

Well I've managed to improve the reflow zone temperature stability by re-writing the embedded software in the oven's main PCB, and using a PIC that actually has some resources (original has no serial port, no interrupts). Having run a load of boards the other day none came out unsoldered or slight cooked like they did before.

I think there's still several issues to resolve though. Just a bit of an ar5e to get to the PCB each time.

[PEP]

Hello

[PEP]

Hello, do you still have this reflow oven? I have one for soldering very simple boards however the SMT HAWK CONTROLLER board is not working. Any help would be much appreciated

[phonoplug]

Hi there - yes I still have it. More specifically whats the problem with yours?

[PEP]

hello, the problem is the PC cannot link to the controller, it tells me to check lead and power. to be honest the wiring has been bodged in places, i am going to rewire it but only after i know the controller will work. all the heating epements work as does the belt, i am waiting for a wiring drg from the manufacturer but that is all the support they can offer. do you still use yours?

[phonoplug]

Ok so the board could possibly be dead. You probably don't need the wiring diagram for the machine. Its fairly easy to work out where the power connects to the main board, and it should have an RS232 cable coming straight from it. If both those are ok then its going to be something on the board that needs attention.

Basically I've re-written the board's firmware for mine as it was pretty awful and there were some massive holes in it. The circuit and PCB designs are no better. The voltage reference for the ADC that reads all the thermocouples was a basic zener diode which has a temperature coefficient thats really not ideal for a reflow oven! There is also a point where a mains live track is about half a mm from the 'isolated' part of the circuit that is directly connected to the RS232 port and therefore the PC. Not good at all. The RS board that controls the belt motor also died on me so I got rid of that and replaced it with a single MOSFET, which to be fair is a much simpler and just as effective solution.

The PC control software is no better either. Its ability to maintain a constant temperature is pretty poor, specially considering thats all it has to do! I've got someone else looking at the possibility of writing a new application that might actually work reliably!

Anyways... as you can guess I don't think that highly of it, but hey, its the oven I have so I've tried to make the best of it.

If you fancy sending the board over to me I'll take a look at it. Before doing that though might be an idea to send me a clear picture of it just to make sure its not totally different! If you haven't already taken it out, you'll need to put the oven on its side, remove the 8 screws holding the plate on the underside of it and take that off. The board is on the inside of the front face of the oven. You'll need to unplug all the removable terminals and connectors (make a note of which goes where first!), unconnect two thick mains wires and either unscrew the triac from the heatsink lug, or if easier unsolder it from the board, leaving it on the lug.

Let me know how you get on.

[PEP]

Hi

I am sure the board is the same as yours. See attached. It has had some tweaking in it life, most noticable a 100k resistor accross two pins on the amplifier (see pic) There was also a break in the track next to this resistor. I checked the resistor and bridged the gap but still nothing. The machine is in good physical condition, i have checked all the heaters/fans/belts etc and they all work, the wiring is a birds nest which i will rectify and one of the main large fuses was blown. My background is not electronics so when it comes to the brains of the machine i am stumped! My company makes retail displays and signage included LED products, this oven is going to be used for soldering very simple SMD LED circuits so although its not very sofisticated i think it will do just fine if i can get it to work!. The main thing is it has a wide belt so i can make larger boards, i do have another reflow oven but the bult is only 200mm wide and controlled manualy. I have spoken to Neli Eveitt whos company used to make them, they no longer do and have very little in the way of info except a wiring diagram. I have the 3 phase model. I picked it up for next to nothing but it is the perfect size for what we need so would dearly like to get it up and running. I would be interested in the new application you mentioned you were looking into.

[PEP]

i forgot to mention that the board is powered by a PSU next to it, the PSU has 3 outputs, one marked 5v and the one is 12 volts and a common. The 5V output goes to the hawk controller and the 12 volt to anothe PCB. When i unplug the controller the output accross the 5v and common terminals read just under 12 volts, when i connect the board the voltage accross the input is just under 2volts dc

[phonoplug]

All the mods on there are standard as far as I can tell. I particularly like the two thick red wires mod where they realised the little thin tracks designed on the PCB were not suitable for carrying the current for zone 6's heaters!

First thing to do is replace that fuse and see if it comes to life fully then, but I guess be prepared for a bit of a bang when you switch on if it blows the fuse again!

Not sure about the voltage readings you made. Maybe the power supply board is duff, but see what happens when the fuse is replaced first.

[PEP]

tried the fuse, one of the sold state relays went bang! But I think that's related to some very strange wiring the previous owner cobbled together.Can I test the board on the bench, ie just a 5v dc power input and the RS232 connected just so I can establish the PC can communicate. Do I need to connect all the ancillaries.? So that broken track is supposed to be there? Yes some very agricultural mods! Thanks for you help on this

[PEP]

It is zone 6 relay that went bang, you think the triac will have been damaged too?

[phonoplug]

Zone 6 (reflow top zone) is driven by the triac hanging off the main board. Unless someone frigged around with the machine. There should be 5 SSRelays which drive the other 5 zones. If you've got things going bang your best bet would be to buzz out across the heater element clusters to check if you've got a short on one of them. I think you can get replacement elements still if you hunt around a bit.

In the mean time though yes just power it up on the bench with 5V, connect it to the PC serial port and it should still talk to the PC fine, just the temperature readings won't be any good as there'll be no sensors connected of course.