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Offline GMDolan  
#1 Posted : 20 May 2021 06:23:43(UTC)
GMDolan

United States   
Joined: 20/05/2021(UTC)
Posts: 2
Location: North Carolina, Wilmington
Has anyone had success in powering 74491 switch motors with DC? Details please.
Offline PeFu  
#2 Posted : 20 May 2021 07:41:28(UTC)
PeFu

Sweden   
Joined: 30/08/2002(UTC)
Posts: 905
Yep, have a look here:

https://www.marklin-user...itching-problem---Solved

I’m now powering all switches, incl. those having 74491 motors, using 20V DC.

Smile
Inspired by Swiss railways SBB and BLS | C and K track | CS2 | TrainController Gold V9
Youtube Channel for the Andreasburg-Mattiasberg layout
thanks 1 user liked this useful post by PeFu
Offline GMDolan  
#3 Posted : 20 May 2021 16:40:40(UTC)
GMDolan

United States   
Joined: 20/05/2021(UTC)
Posts: 2
Location: North Carolina, Wilmington
Thanks for the quick response to my inquiry. Have you measured the current draw at 20VDC?

I plan on testing 15 to 24 VDC. With success I'm likely to build custom PCBs to power my turnouts. I want to investigate DCC++EX control software to see how best to integrate turnout and signal control with that software ecosystem.
Offline JohnjeanB  
#4 Posted : 21 May 2021 00:34:59(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 1,757
Location: Paris, France
Originally Posted by: GMDolan Go to Quoted Post
Have you measured the current draw at 20VDC?

I plan on testing 15 to 24 VDC. With success I'm likely to build custom PCBs to power my turnouts. I want to investigate DCC++EX control software to see how best to integrate turnout and signal control with that software ecosystem.


Hi
Measuring the current is difficult with a multi-meter because the pulse duration needs to be very very short (100mS or so) so only using a resistor and an oscilloscope.
Working with DC, calculating the current is easy: measure the coil resistance (the only factor to limit the current in DC operation). Then I=U/R (as we all know)

Märklin decoders like the 6083, 60832 work in hashed DC voltage (19 V DC) so the difference is that the coil inductance comes additional to its resistance to reduce the current.
I would not advise operation above 20 V DC because, on a good solenoid the force is already ample enough. Yes you may get more force but increasing the voltage (25 VDC) and logically reducing the duration (50mS) but it would produce a force and a shock for which the Märklin switches were not designed for (You will destroy them).

Note: Märklin is aware of this trend to short-circuit the protection switches as they have reduced the minimum duration on CS2 and CS3 to 100 mS (it was 200 mS a few years back) which is ample enough to have a very reliable operation.

Cheers
Jean

My layout videos
latest vid
hump yard
Offline hxmiesa  
#5 Posted : 21 May 2021 06:52:30(UTC)
hxmiesa

Spain   
Joined: 15/12/2005(UTC)
Posts: 3,295
Location: Spain
I use 24Vdc. I have programmed my system to activate the pulse for 0,1s.
I give each movement 2 pulses(!), as sometimes the switching is so hard that the mechanism seems to bounce back a little. The 2nd pulse leaves the relay in its right place.

I thought I would be having a magnetisation problem in the long run, but after 15 years this doesn't seem to be a problem. (I´m using K-track switch motors, both old and new)
Best regards
Henrik Hoexbroe ("The Dane In Spain")
http://hoexbroe.tripod.com
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