Toroidal power supply and Gecko stepper questions

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19 May 2021 04:10 #209439 by rodw


Only problem I had initially was the current draw when I turned on the power to the toroidal was too much for the circuit breaker I was using and it would trip. I replaced the circuit breaker with a "D"curve breaker and all is well.


This can be solved by adding a Thermistor that prevents the inrush. As it gets a bit hot, the thermistor resistance falls so the current increase is gradual. When I put in my toroids the supplier gave me a couple and I never trip a circuit.
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19 May 2021 11:08 #209482 by tommylight
15A termistors ???
That would require an RC timer and a relay, nowadays used on all the high power electronics even the chinese CO2 welders have it.

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19 May 2021 12:13 #209492 by Clive S

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19 May 2021 13:04 #209501 by rodw

15A termistors ???
That would require an RC timer and a relay, nowadays used on all the high power electronics even the chinese CO2 welders have it.


Nah, super simple when th eguy designing th etoroid is speccing the thermistor

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19 May 2021 19:53 #209542 by PCW
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19 May 2021 21:35 #209549 by rodw

This kind of thing:

www.digikey.com/en/products/detail/ametherm/SG32/4862345


Yes exactly. I thought it was a cool trick

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19 May 2021 21:49 - 19 May 2021 21:49 #209552 by rodw
Shown here installed. Here we used 2 x 32 volt toroids because they were available. 64V 20 amp out. No need for any other circuitry.
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Last edit: 19 May 2021 21:49 by rodw.
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19 May 2021 22:40 #209563 by txtrone

Shown here installed. Here we used 2 x 32 volt toroids because they were available. 64V 20 amp out. No need for any other circuitry.


Rod - What motors are you running? Are you using all the same motors and LAM drivers? Or do you have a mixture?

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19 May 2021 22:46 #209566 by andypugh

This can be solved by adding a Thermistor that prevents the inrush.


I have not had much luck with thermistors, but it is pretty simple to do it with a resistor and a relay if you add a bit of magic. And that magic is HAL.

What my lathe does is power the DC PSU through a 250W power resistor. It helps that the 8i20 drives report-back the bus voltage. (as does the STMBL). But this could just as easily be a software timer.
Once the bus voltage is near the nominal value, HAL sends an output to turn on a relay that bypasses the resistor.

Note that the resistor is not nearly big enough to run the machine full time, if the relay fails open-circuit then the resistor will too. But that's unlikely as they typically fail closed-circuit and then all that happens is that the RCD trips next switch-on.

My mill uses a custom 555 timer circuit. But only because I was younger and stupider.

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19 May 2021 22:47 #209567 by thefabricator03
I like how the thermistor is installed into the terminal. It makes for a clean installation.

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