View Full Version : Industrial application
02-03-2007, 09:12 AM
I have just installed two machines for trial in the plastics industry - built around the propellor.
All working according to plan with some minor teething problems.·3 phase here is 380 - 415vac - I have noticed that the prop·has 'reset' itself after switching in contactors even though the lines are filtered and suppression units are fitted accross the coil. It is not the coil on the contactor - this was tested by removing the 3phase supply line and switching the contactor - besides the contactor coil is 24vdc and is switched by a optoisolated photovoltaic (ssr of sorts) with inbuilt·reverse biased diode. So if I manually switch the contactor with supply and load attached - the prop resets - so it is picking up transients from the inductive load being switched. The prop board is supplied by a 24vdc industrial power supply with dual onboard regs. I·am putting on a·filter on the load side tomorrow and am pretty sure that will sort it . I have used stamps·in industrial applications switching contactors with higher loads and have not had·this issue -·· just thought I would bring it up·here..
02-03-2007, 07:06 PM
A line filter in front of the (on the AC line) powersupply could well do the trick as well.
Inductors and capacitors are usefull components as well .
Separate the 24VDC used to switch the contactors (24VDC)
It is common to use a separate supply for input and output devices in industrial applications.
We normally use a 24VDC supply for all the outputs .. contactors.. solenoids ..etc etc
and a separate supply to power up PLC or micro controller cards.
Line filters made by people like MTL surge ,Shaffner and Corcom are some of the industry leaders.
It is also good practice to make sure that cabling is routed correctly..
Keep us posted as to what you have found and what you did to fix it.
Each application is different .. but there are basic rules as a good starting point.
Rgds Ronald Nollet Australia
02-03-2007, 07:56 PM
Is the programming RS232 connector plugged in when this is happening? I'd look at the reset pin with a scope while you are switching a load. Maybe even pull the reset pin straight to Vdd as a test. Depending on the circuit you used, the reset could possibly trip off a very short transient.
02-03-2007, 08:12 PM
coils pick up transient voltage, there are "free energy" devices on the web that use this technique, they work great around high power lines, but do not work at all in the desert... anyway, check the phase, isolate, and filter. you should be ok.
02-03-2007, 08:24 PM
A line filter in front of the (on the AC line) powersupply could well do the trick as well.
Rgds Ronald Nollet Australia
Can you recommend where to get or make this "line filter" that you recommend.
I have problems with relay switching as well.
02-03-2007, 10:48 PM
A·simple polorized capacitor or ceramic capacitor is a very good·and the most used voltage filter.
Post Edited (bassmaster) : 2/3/2007 2:55:17 PM GMT
02-04-2007, 03:11 AM
Bassmaster - all that was tried - the problem was solved as I thought with the line filter on the inductive load side of the contactor.
OzStamp - Never had the need to seperate the 24v supply between contactors and control - Usually only use 1 24vdc PSU for both - the application switches off a third party conveyor system with no filtering - so I fitted the line filter on the output side of the contactor as suspected and all was fine. The 24vdc psu has already an inbuilt line filter. Have built approx 40 different machines using this method.Obviously I have ensured cable routing is appropriate for such applications.
originator - no not connected - looked at the reset pin - nothing appreciable there - sorted as stated.
I didn't expect it to be a problem but thought I would mention the fact that the Prop seems more prone to transients than a PLC or Stamp in such applications..
Thanks for the 'feedback' though - excuse the pun !
Post Edited (QuattroRS4) : 2/3/2007 7:29:58 PM GMT
02-04-2007, 04:43 AM
Its good to mention any issues you find,
As first generation chips go, it does not surprise me that it may have some undesireable issues, I noticed that the prop clip "powers" the prop using the education solderless breadboard setup schematic, but not on my demoboard? I think its from the tx lead or a design difference in the dip package.
Your stamp was probably more forgiving, as it has been through a few revision changes.
For the price though I have not found any major issues. I can run 6 Tokheim gasoline pumps (probably 32 would work also, at 200ms polls in the lab at RS232 with a bnb 232/422 converter, display the poll data on pocket tv remotely, one pin for an LCD status/controll display, the keyboard to auth the pumps/read sales/price the pumps, etc, an SD card to store a logfile, all in 5 cogs and 3/4 of available ram, and all but a few objects in spin. A little more work and I can add Card reader control and have a near complete fuel control solution for a gas station to control the fuel sales!
Total cost in parts, under 50 bucks and a few existung spare parts.
I bet I can get the 422 out of the prop soon with asm, and use a serial connection to a POS system to remove the LCD/Keyboard/tv/and sd. and run in 3 cogs, Then the total cost with a metal black box with a power supply would be under 50 bucks.
Amazing stuff for 20-30 hours of coding and a few bucks in parts. Parallax has moved into a whole new level with this chip. Thanks for finding this issue, Ill make sure I filter more when I order the pcb with eagle.
The prop coould revolutionize automation and control in many industries.
02-04-2007, 04:50 AM
Yip - couldn't agree more - have already replaced multiple P.C.B control units on various machines with a single prop based P.C.B - bring on prop 64 ! I have an application waiting in the wings !
02-04-2007, 08:09 AM
Transients are more an issue of the technology, the prop is a 3V3 part compared to 5V for the stamp.
Lower voltage transients that don't worry a stamp could affect the lower voltage prop.
Even newer parts at 1.8Volts like the next version of prop? More consideration will be needed to keep transients out of the board.
EMI filters, inductors, transorbs, R/C networks are all needed in todays lower voltage pcb designs.
Ground planes and ground fills and a bunch of stuff helps with EMC/EMI.
There is a big difference between 4Mhz 8 bit micro made in 1-2 micron fabs to 0.09? micron 80MHz 32bit cpus.
The packages themselves may need faraday cages around them, smaller technology makes for better radio receivers;)
02-04-2007, 09:16 AM
Great to hear you have it sorted.
Eliminating noise is not a black art but certainly can be a very testing issue especially when your adding stuff
to an excsiting control system. An dealing like we do with Motion Control applications high speed encoder feedback
and resolver signals into servo/stepper controllers we normally start with all the basic rules as mentioned in my previous
post in the topic.
Putting the Line filter as you mentioned on the switched side of the contactor eliminated the problem
So if I understand this correctly this filter filters the ac to the load ..
And gets rid of the problem ?? If this is all assumed correctly it could well point to the fact that the
filter in the PSU is not doing its job as suspected.. have seen that before..
There are many PSU units on the market predominantly siwtchmode type they seem to have "inrush current limiting"
and "Simple filtering" methods build into them.
I recall a job sometime ago .. we had a similar problem.
The DC supply cable from the PSU to the controller we were using was picking up induced rubbish on it.
Ended up using a shielded cable that we had and took the screen to Earth and the problem disappeared.
Ronald Nollet Australia
02-04-2007, 01:18 PM
Is the industrial power supply a switching type? You might consider a linear supply such as Sola or Condor. They are larger and look kind of old school, but they have a built in transformer and beefy caps to isolate and filter much better than the newer DIN rail style supplies.
02-04-2007, 01:50 PM
Good point "Bill Sturm"
It seems that all around the world all major automation component suppliers are all offering Switch mode type Din Rail mounted supplies .. They do have very little filtering in them.
These day's it seems that stuff needs to be cheap for it to sell... they forget key issues like nosie filtering
We are seeing that here "down under"... 3 years ago a 24VDC 5 AMP dc supply would cost $200-300
Now they are down to $50 -60 ( OZ Dollar about 40-45 US ) .. some of the wholesalers inflate their prices to ridiculour prices
so that they can give 50-60 % discount...
They all come out of China .. I know 4-5 different types and for sure all made in the same factory.. different label
The funny thing is that some people spend very little on a PSU .. when they find out they have a problem
they spend money on Line and Surge Protection type of stuff..
As Bill Sturm suggested the old Condor type PSU units are good ..the trafo is a fantastic CHOKE for high freq noise.
Ronald Nollet Australia
02-04-2007, 02:03 PM
Yes boys it happens to be a switched mode - but proclaims filtering - also have had issues with claims ! but this very psu has been used in various apps before without issue . Siemens SITOP - you all know the deal ..
I do appreciate the feedback though..
Post Edited (QuattroRS4) : 2/4/2007 6:09:25 AM GMT
02-04-2007, 02:13 PM
Aware of all that - I just wanted to point out an experience..
02-04-2007, 03:25 PM
The fact that a powersupply has a certain name on it... does not mean it works well everywhere.
The fact that it may come out of Europe and is build by our German friends normally tells us that
is pretty good stuf.. read any good documentation that goes into detail about filtering .. cable spearation issues etc etc
it will alway's mention the use of a Line Filter and some sort of surge protection.
The local car manufacturers here in Australia demand very extensive line filtering and surge portection
when your doing a control cabinet for them.
I have seen stuff that has worked for years in a certain place ..being shifted to a different location in a plant.
Suddenly it has all sorts of problems .. all due to noise .. locally installed inverters ... spotwelding robots
The more we share this sort of stuff is kind of neat.. alway's learning that's for sure.
02-05-2007, 02:17 AM
Interesting that you say that Oz - I decided to play a bit today - contactor in same place swapped l1,l2,l2 (3 phase supply) and t1,t2,t3 (3 phase to load) - so put supply to t1,t2,t3 and load to l1,l2,l3 - same cable routing and removed filter - while it still reset it did so about half the amount of time !
The particular PSU I mentioned has worked in seriously 'noisy' environments with much larger inductive and reversing loads with out issue - decided to try put a filter on the supply to the psu and remove from load - I still had resets. So I put a filter back on the inductive load and all was well again ... might check out that motor though .. as it is only a fairly small motor to be causing this.
Decided to put one of my stamp based controllers in - just to switch on/off the contactor without the filter in place and it did not reset. I put it all back as was again - i don't think I will be allowed to play with it anymore ! - always a good sign !
There in lies my final chapter on this one - but if I happen upon something else I will certainly post it here guys..
02-05-2007, 06:39 AM
My small 9" LCD on my mill used to lose it whenever I ran the mill at full speed, made it hard to see TurboCNC.
Fix was large ferrite bead on VGA lead and another on the cable to the motor, the clip on type about 1" dia 1.5" long.
I had already moved to filtered plug power boards, so maybe you need to do something with the cabling as well.
02-05-2007, 01:57 PM
Gavin - as suspected the filter sorted it - they have been flat out since - doesn't look likely that I will be 'allowed' near it anymore - all is well.
02-05-2007, 05:25 PM
So what does the controller do.
I figured the prop will make a kickarse controller for replacing old worn out boards.
Simple PLC? Built in basic?
02-06-2007, 02:50 AM
Many controllers I have built are control box replacements for machinery with added datalogging and coms to production management systems. Completely in house designed machines from automated print and apply machines - precision grinding machines, automated assembly units. These two prop based machines are high volume counters for filling prescribed quantities of product into boxes and indexing to next box when complete. I will post details shortly - if customer gives the go ahead.
Some of the machines require a .NET front end GUI and automated SQL database updating with all machine control handled by stamp/prop/javelin - I kind of bypassed the SX series for some unknown reason - but I will get back to that at some stage. I stopped using PLC's years ago. I have a number of boards designed which just need to be programmed to suit the specific task at hand.
The reason a prop was chosen for this app was 1) a large screen was required 2)found that the stamp was not able to handle the volume of product accurately - up to eight lanes of products to be counted at high speed at the same time - was getting inaccurate counts with a stamp and javelin - tried a few variants - with shift registers etc - close but no cigar !
Besides the serial coms were slow on stamp - milliseconds to do a 'serout' to update screen and bang may have missed 10 products going through. Javelin was closer but not 100%.
First go with the prop with VGA screen and accuracy was 100% - choice made for this application.
That said I still have multiple applications for the stamps - just depends on the nature of the application.
You could say that stamps are expensive for this - but I have a shelf load of P.C.B's ready - so dev time
is pratically nothing and turn around is fast - critical when dealing with large volume manufacturers. Allied to this - a nice professional P.C.B is good advertising and has created 'knock on' business. Any potential problem is quickly identified and sorted - because the p.c.b is my own design...... that said the only problems I have had have never been the control p.c.b !! - Just the usual - contactor,motor,relay,ssr etc - basically 'wearing' parts.