Retrofitting a 1986 Maho MH400E

14 Jan 2019 00:35 #124125 by J Green
Mark Some of my thoughts .............. The Phillips 432 control used a switching power supply + 6 volt battery (memory back up ) for the computer an control boards. So switching power supplies can be used, but there can be big differences of say a switcher designed for some industrial use vers one designed for say consumer / home use. Do I think switchers are a good thing = very big Yes .
Do I know your switching power supplies are causing a / the problem = No . Consider that I am a old analog geezer and that is what I am more familiar with . EMI shielding ........ yes it can help , but my thought would be to reduce the amount of or remove the source of EMI generated. I have used a portable ( battery powered )AM radio to get some feel/value as to amount. VFD drives are just evel. The indromat servo drives you/we have use SCRs , and they generate some EMI noise also. Might try looking at scale error of just moving Y axis only an also see if the Y axis servo motor wires are close to the scale wires. Might check the shield wire of Y axis servo motor wires.. I wonder if there is Y axis scale error when only the Z and/or only X axis are moving may have tried that, I don't remember.
My thought , If the 5 volt battery lash-up makes a difference then consider making up a analog supply using say a 7805 Ic
maybe even consider also using a 78xx series Ic for 12 volt DC. No I don't think ITX power supplies are good enough for Real DC,
The Maho has a 24 volt DC supply , might be able to use that as a DC source for a cascaded 12 volt an then feed a 5 volt regulator Ic Pro = saves needing a 240 volt to say 10 volt transformer + rectifier for a analog supply. Con = having a single phase 240 volt input would increase isolation and could be powered up with extension cord/wire for checking of circuits/troubleshooting. Suggest you bounce this off Mr. Hanno for his input. What size Maho is he converting ? any chance you could drag him onto this thread?
I have a Siemends "STOP modular 20A - 24 volt -120/240 rail (DIN ?) mount " switching supply from e bay. The specks looked good enough for me to try it ,but as of yet haven't done so . Siemends makes high to low quality stuff , but usually have product information on their web site. Might try finding one of their supplies on the used market.

Tracking down electrical noise issues can be a very deep rabbit hole and your circle program showing the repeatable Y axis scale input mess-up is a huge help. That is why I wonder if moving X an Z axis only, will give the same Y axis scale mess-up ? Your neat circle program
if the size of the circle is smaller would that change the number/amount/position of Y axis errors? Could point to break in a wire or shield wire. Do you get the same results if the control cabinet door is wide open ? EMI temp. shield ---- I have used aluminium cooking foil covered with plastic film and a clip lead wire for testing stuff .
To me,your trouble shooting steps look very useful . Now it's the time suck job of crawling around in that rabbit hole trying to find real repeatable cause an effects.

Hope you nail the real problem source. Keep us current on this misadventure
The following user(s) said Thank You: RotarySMP
14 Jan 2019 08:12 - 14 Jan 2019 08:28 #124143 by RotarySMP
Thanks Bob, Your advice in this area is greatly appreciated.

Yesterday I got as far as switching Y and Z's exe's (remember the Z axis EXE is the stand alone unit with differential output). The problem followed (now on Z).

The behaviour is similar to that which I thought I had solved with more voltage (flat batteries posts a few pages back). For the first few few minutes it is stable, then it starts moving in steps (you can hear the change in frequency as it moves - this is with no motion commanded), and after about 20 minutes, it is moving constantly. This is in the video from 1:20.

I added up the loads on that crappy chinese PSU which is rated for 2.4A, and ist has the three encoder bulbs of 120mA each + three EXE electronics at 140mA each (although not sure on that as the recycled three axis EXE also has 12V supply, which I took off the ITX PSU), then the Logitech powered USB hub, the ELU Monitor Touch stuff, and the Blue tooth adapter for the keyboard are all on it.

Lets say 1A at 5V, I was wondering what batteries I can use. But I still have the 6V lead acid batterys removed from the MAHO, so I'll throw them on a charger and see if they have any life still in them, and add a dropping resister to get 5V.

Last edit: 14 Jan 2019 08:28 by RotarySMP.
14 Jan 2019 08:22 #124144 by tommylight

RotarySMP wrote: But I still have the 6V lead acid batterys removed from the MAHO, so I'll throw them on a charger and see if they have any life still in them, and add a dropping resister to get 5V.


You can use 4 NiMh batteries as they will give exactly 5V (1.25V each), and they are cheap and rechargeable. I would not recommend recharging them while in use as they require 1.4V each for charging, getting to 5.6V total.
Do not use resistors for voltage regulation on dynamic loads, use 2 diodes in series, it will give a 1.2V voltage drop and be stable enough for what you need.
The following user(s) said Thank You: J Green
14 Jan 2019 08:33 - 14 Jan 2019 10:12 #124145 by RotarySMP
Thanks for that. I have NiMH AA's. I think I have nominally 800 mAh ones, so they should work for up to an hour.

Cool, I can 3D print the holder:
Last edit: 14 Jan 2019 10:12 by RotarySMP.
14 Jan 2019 12:20 #124151 by tommylight
Nice holders, i need to finish a 3d printer i started several years ago !
14 Jan 2019 15:01 #124156 by RotarySMP
You should. They are very helpful.
14 Jan 2019 15:35 #124160 by tommylight
At the time i could not think of anything useful to make with it ! Still don't, but i would like to have it finished.
14 Jan 2019 16:51 #124166 by RotarySMP
I am not a big fan of plastic stuff, but once you have a 3D printer, you would be suprised at the problems which pop up which it can solve.
The following user(s) said Thank You: tommylight
15 Jan 2019 19:16 #124260 by Mccartymachine1
I am retrofitting a mh600c. Can I get some info on your connections between the 7i77 and the 3trm2? Also if I could get your PID settings to give me a place to start. Thank you.
15 Jan 2019 19:52 #124262 by RotarySMP
My PID settings are posted about 10 pages back. Since there is no PM on this forum, please PM me on or (same user name), so I can send you my wiring diagrams.
The following user(s) said Thank You: Mccartymachine1
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