Re: Computer Power Supply and Turnout Problems


When I wanted +/- 12 for tortoises (up to 60 of them), I simply bought two 12V, 3A power supplies on the surplus market (link to a similar product follows).  Tie the + of one to the - of the other, and you're away to the races.

Computer supplies are not really set up to provide lots of current on the 12V outputs without any demand on the 5V rail, if my memory serves at all.  Besides, it's overkill, probably needs a fan, and in general is using a sledgehammer to swat a fly - the fly is gone, but so is the window! 

On 2019-10-07 17:01, Wayne Swearingen wrote:

I have a 350w computer power supply that I am using for turnout motor control. I bought one of those adapters that plug into the motherboard pigtail and break-out 12v +/- 5v and 3v

There are currently about 18 stall motors connected to it, not Tortoise, the plain black stall motors. With everything hooked up the negative side of the power supply drops down to about 9v which causes problems with points since we have around 1k ohm resistors soldered in place on each motor. 
I've read up on the majority of the stall motors and the consensus seems to be 20 mA as the rule of thumb per motor. I did confirm and saw that the negative side of the power supply is only putting out .8 AMPS while the positive side puts out considerably more. By my math 20 mA x 18 motors doesn't put me in danger on the negative side but something is pulling the volts down.

I really hate to have to un-wire one side of each motor to narrow down where the problem is coming from. Does anyone have any experience with the computer power supplies for turnout control? Maybe its a bad adapter board? It was only $9 on amazon so I don't have a whole lot of faith in it. We used to have this archaic variable positive/negative power supply which worked fine. I removed it after we upgraded the layout to DCC, this thing had to be a fire hazard with all of its components mounted to plywood and big heat fins. It's quite a sight. 
Does anyone have any recommendations for a reliable +/- power supply? One that doesn't need an adapter possibly? I've read up on converting the computer power supplies without the adapter board, I was just hoping for a nice clean look with the adapter. 


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