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Wiring a crossover with tam valley servos

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Wiring a crossover with tam valley servos
Posted by IDRick on Wednesday, August 14, 2019 12:12 PM

I'm builing a test switching layout that will eventually be a part of a larger layout.  I want to use caboose hobbies switch machines for single turnouts and Tam valley servors for crossovers.  I want an easy functional crossover that is pretty much plug and play plus at a lower cost than a tortoise setup.  What do I need to order from Tam Valley?  I will not be controlling turnouts with DCC.  Thanks!

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Posted by gmpullman on Wednesday, August 14, 2019 12:21 PM

Just the two servos as far as I can see.

https://www.tamvalleydepot.com/products/servosaccessories.html

Plus a double pole double throw toggle switch to act as a reversing switch to provide reversing DC power to drive the servos. Maybe their DY-5001 DPDT relay would make wiring the servos easier? 

If you are powering the frog you would get the servo model with the add-on snap-switch.

Good Luck, Ed

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Posted by CNR378 on Wednesday, August 14, 2019 1:38 PM
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Posted by IDRick on Wednesday, August 14, 2019 2:05 PM

Thanks Ed!  I very new to this...

Seems to me that I would need the following (but clearly could be wrong):

    2 Singlet servos,

    1 fascia controller (FCB020), 

    1 recessed fascia mount MFC3D1

    1 y-cord to operate both turnouts with a depressing the controller  SRX003

I don't see how they are powered?  Can you tell me?  Thanks!

Based on my understanding, I'm looking at $21 per crossover.

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Posted by IDRick on Wednesday, August 14, 2019 2:07 PM

CNR378

 
Thanks for the link. How are the servos powered?
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Posted by RR_Mel on Wednesday, August 14, 2019 2:23 PM

I use the Tower SG90 servos and they run on 5 volts, they can draw up to 100ma depending on the servo load.
 
 
Mel
 
 
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Posted by CNR378 on Wednesday, August 14, 2019 3:00 PM

IDRick

 

 
CNR378

 

 
Thanks for the link. How are the servos powered?
 

 

8-24V DC

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Posted by IDRick on Wednesday, August 14, 2019 3:38 PM

CNR378

 

 
IDRick

 

 
CNR378
 
Thanks for the link. How are the servos powered?
 

 

8-24V DC

 

 
Sorry, I'm a complete newbie to this system of turnout control.  I should have gone directly to tam valley, explained I'm a complete novice relative to their system, and asked their advice.  I don't know where and how the Tam Valley products connect to the power supply.  My question was way too basic to ask on this forum...  Apologies
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Posted by BigDaddy on Wednesday, August 14, 2019 4:25 PM

IDRick
I want an easy functional crossover that is pretty much plug and play plus at a lower cost than a tortoise setup.

Easy, plug and play, and low cost doesn't really happen.

I don't think you should apologize.  The Electrical Cognescenti know how to build this with $10 of parts from Ebay.  You just need to get one of them to spell it out.    I'll be standing by ready to take notes.

edit for spelin

Henry

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Posted by RR_Mel on Wednesday, August 14, 2019 6:52 PM

The SG90 servos are powered by 4 to 6 volts or nominal 5 volts.  They can be driven with many controllers available, I prefer using an Arduino but I also like the Tam Valley controllers.
 
I also use the SG9 servos and the Micro 7G servos for automation.  For their cost the Tam Valley looks pretty good and simple to install.
 
 
 
I’m using the 7G servos for door automation.  At less than $1 off eBay they go a long way.  They are small enough to fit in the overhead above my roundhouse doors for opening and closing the doors.
 
It’s rather easy to automate figures with the servos.
 
 
 
 
 
 
 
Mel
 
 
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Posted by rrinker on Wednesday, August 14, 2019 7:28 PM

gmpullman

Just the two servos as far as I can see.

https://www.tamvalleydepot.com/products/servosaccessories.html

Plus a double pole double throw toggle switch to act as a reversing switch to provide reversing DC power to drive the servos. Maybe their DY-5001 DPDT relay would make wiring the servos easier? 

If you are powering the frog you would get the servo model with the add-on snap-switch.

Good Luck, Ed

 

NO NO NO

Servos don't change direction based on polarity like a Tortoise. Nor do they like to be stalled like a Tortoise. Understandable to get this wrong, since MR published an article a couple of years ago saying to do exactly this, although it required modification of the servos. But they get very hot if stalled, and I can;t imagine them lasting long used as a stall motor, they aren't meant for that.

 Most of the Tam Valley controllers will drive 2 servos - so a Singlet plus a second servo would work for a crossover. If there are more than one crossover to control, the Octopus may be the controller, it can control up to 8 servos, serveral can be doubled up but not all 8, for crossovers. 

                                    --Randy

 


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Posted by gmpullman on Wednesday, August 14, 2019 8:51 PM

rrinker
Servos don't change direction based on polarity like a Tortoise.

Didn't intend to steer the OP wrong. He was asking for non-DCC control and that's where I thought the DY-5001 would drive the servos.

I stand corrected Embarrassed  Ed

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Posted by RR_Mel on Wednesday, August 14, 2019 9:07 PM

I missed using the servo like a Tortoise and agree with Randy that is a NO NO!!!
 
When a servo is in stall mode it will draw high current, can easily draw over 80ma.  The SG90 servo gets hot at 40ma and in less than 5 minutes will be hot enough to ding the servo housing. 
 
I highly recommend the Tam Valley No-Buzz In-Line Servo Quieter, that can make or break using a servo to control turnouts.  It will stop the high current to the servo when stalled.
 
The servo stall current was the hardest part of me using servos for my turnouts.  I wanted to have the servo keep pressure on the points against the outside rails and doing so the current was to high and the servos got supper hot at 40ma.  Adjusting the servo driver to be at a low idle current prevented the servo from applying pressure against the point rails.  The No-Buzz In-Line Servo Quieter, lets the servo apply pressure then drops the servo preventing the high current until the servo drive is changed.
 
Using servos for turnout control is much cheaper than a Tortoise.  I paid $1.50 for the servo, about $1 for miscellaneous parts and $4.50 for the Tam Valley No-Buzz.  A single $10 Arduino MEGA will control over 20 turnouts.  Another feature of Arduino control is the speed of point travel, it can be adjusted from super slow to instant.
 
 
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Posted by IDRick on Wednesday, August 14, 2019 10:38 PM

Thanks, this has been somewhat helpful (remember I'm a total newbie on this topic).  My whole thought process on this was simple.  I had read a post of Randy's where he talked about using Tam Valley components to control a turnout.  Randy has helped me times and never steered me wrong so I thought, I ought to give this a try.  I did some reading on the Tam Valley Depot website which gives some general direction but would benefit (IMO) with a practical example showing all the components needed for a simple single crossover and how everything goes together.  They could convert me to a "true believer" but I need to have a practical example from A to Z for the simple before moving on the complex (controlling multiple crossovers, yard ladders, etc).  Mel has given a good start.  I prefer to start with Tam Valley based on Randy's recommendation that it is an easy system for beginners and essentially plug and play.  $20 to $25 for the first crossover would not be cheap but would be awesome as a learning experience.  Right now on my existing layout I use two caboose hobbies ground throws at each crossover and want to change!

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Posted by rrinker on Thursday, August 15, 2019 7:38 AM

 Still cheaper than Tortoises - unless you rig a rather complex mechanical arrangement to use just one, but then you could do the same with a servo and save money there tooo.

 The quieter modules aren;t strictly necessary - if you set up the travel when programming the Tam Valley controller, the servo shouldn't be stalled. Plus some of the newer versioons they have already have that built in to the controller. I used the older Singlets, the ones where the fascia controller was the whole circuit, and none of my servos buzzed after lining a turnout. 

 My DIY Arduino based servo drivers for my new layout will have the same auto shutoff at end of travel so they don't buzz even if not totally aligned, as long as the servo get reach the programmed end position, power will then be cut off. Technically the signal gets cut off, but with no signal telling the servo to move to a certain position, it won't fight back against being moved slightly by the force of the piano wire.

                                    --Randy


Modeling the Reading Railroad in the 1950's

 

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Posted by RR_Mel on Thursday, August 15, 2019 8:27 AM

rrinker

 

 My DIY Arduino based servo drivers for my new layout will have the same auto shutoff at end of travel so they don't buzz even if not totally aligned, as long as the servo get reach the programmed end position, power will then be cut off. Technically the signal gets cut off, but with no signal telling the servo to move to a certain position, it won't fight back against being moved slightly by the force of the piano wire.

                                    --Randy

 

Randy please post your no buzz sketch for the Arduino.   
 
 
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Posted by rrinker on Thursday, August 15, 2019 12:42 PM

 I did, a while back. It's now completely wrong, as I discovered trying to lay out a PCB for it, it was easier to change which pins I used for what input or output than trying to route lines around one another, so the curent code no longer matched the pin assignment.

 But really all it's doing is servo.detach() after the servo reaches end of travel. I have a constant for minimum position and one for maximum position, the the move routing keeps moving the servo until the current position is at or less than the minimum or greater than or equal to the maximum.

                                            --Randy


Modeling the Reading Railroad in the 1950's

 

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Posted by IDRick on Thursday, August 15, 2019 2:47 PM

Mel,

What do you use to power your arduino controller?  Which arduino controller are you using?  What mounts do you use to attach your servos to the layout?  What is the process to control two servos on a crossover?

I've been looking at alternatives with Tam Valley Depot and they pretty expensive.  If I used an OctIII to control 8 servos, it would cost $31 for the OctIII, $80 for the servos + mounts, and $40 for the fascia controllers.  Plus another few bucks for servo extensions.  Seems to be too expensive for me.  I'd like to look at alternatives.

Thanks,

Rick

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Posted by RR_Mel on Thursday, August 15, 2019 5:08 PM

Rick
 
I pretty much buy all my supplies off eBay as there isn’t a model railroad hobby shop here, the last store that stocked model railroad stuff closed 8 years ago.
 
There is one good RC store that stocks a good supply of Evergreen Styrene, Basswood and K&S Brass.  He can order HO stuff from his LA Distributor with a several day delay.
 
I buy the Tower SG90 servos off eBay 10 for $15 and Arduino UNOs for under $6, MEGAs under $9.
 
The drawing on my earlier post shows my Mel servo mounting bracket, I don’t have anything against the Tam Valley mounts I simply like to do it my self.  The servo is $1.50 the mount about $1.  eBay connectors are about 20¢, $2.70 isn’t too bad for a turnout machine.  A MEGA at a little over $8 will control all of my turnouts, I also use Mel made Arduino expansion boards to interface between the Arduinos and servos as well as the toggles for control.  That runs up the cost to about $20 or $1 per turnout plus the $2.70 for the switch machine, total cost less than $4 per turnout vs $17 for a Tortoise.  
 
I use 12 volt switching power supplies off eBay to power everything on my layout except my trains which are regular MRC DC & DCC power packs.
 
For voltages less than 12 volts I use DC to DC converters again off eBay.  I have two sizes of switching power supplies, 12 volts at 15 and 30 amps.  I have a lot of accessories.  The DC to DC converters I use for my layout are rated 8 amps ambient cooling 12 amps fan cooled.
 
Currently I have approximately 300 1½ volt 1mm bulbs and 500 2.5mm to 4mm 12 volt Grain of Wheat bulbs on my layout.  I have a 8 amp DC to DC converter adjusted to 1.4 volts for the 1mm headlight bulbs, a second converter adjusted to 8.5 volts for structure lighting (70% for increased bulb life and more realistic lighting).  Both runing at a little  over 6 amps.
 
I have a third converter adjusted to 5 volts for every thing requiring 5 volts.  I actually have a total of 6 DC to DC converters running off the switching power supplies, so far the load doesn’t draw over 8 amps from the converters so I don’t need a cooling fan for them (Yet).
 
I will eventually have 21 turnouts powered by servos and the cost at this point of the project should be about $80 for all 21 thanks to Randy’s help on the servo detach().
 
I have about $100 tied up in my power supplies, two 15 amp and one 30 amp, a total of 10 DC to DC converters.  That includes the power for my workbench for testing and building up my goodies, $100 for 60 amps for the 12 volt main sources and up to 30 or so amps of miscellaneous voltages. 
 
Actually is a bit more, I also have a slug of digital volt and amp meters also off eBay.  I have a volt meter on every voltage for easy reference, about $3 each.
 
I only buy things like extension cords if absolutely necessary, I make everything myself.  I stock all kinds of connectors and wire again off eBay.  Making your own stuff cost about 5¢ on the dollar.
 
I’m a gadget guy and I love dinking around with anything model railroad related.  I spent my entire working career (49yr & 10 mo) in electronics and I still love working with it.
 
 
Mel
 
 
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Posted by rrinker on Thursday, August 15, 2019 6:27 PM

 Yeah, that's the one thing Tam Valley is high on - the servos themselves. They are insanely cheap on eBay. You can buy just the mounts for under $5 each from Tam Valley, or just can just glue the servo on its side under the layout - you don;t really need the fancy mounts.

 It's still cheaper than Tortoises. The Octo comes out to less than $4 per turnout, the servo and mount at Tam Valley's price is $9 each, so you're at $13 per turnout. A Tortoise is at least $15 in 6 packs. You still have to add the toggle switch and LEDs to get anything like the equivalent of the fascia controller - though the Octo can use a simple toggle as well, you don't need the fancy fascia controllers. If you get the servos on eBay for about $150 each, the mounts are $6 each, so $7.50 for a servo and mount, plus $4, $11.50 per turnout. Much better than $15+ per.

 And for DIY, Geoff Bunza has step by step instructions for setting up an Arduino - you don;t need to know anything about it, his instructions tell you how to load the software and use his existing program on it to then connect servos with buttons or toggles. You can get a suitable Arduino for under $10, I think Geoff's design that uses buttons drives 6 servos. So $10 for an Arduino, $9 for 6 servos, $36 for 6 mounts. Little over $9 per turnout! And there are cheaper mounts than the ones Tam Valley sells. Iow Scaled Engineering has ones that are $15 for a 6 pack of mounts. That works out to under $6 per turnout for 6 of them.

                                       --Randy

 


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Posted by IDRick on Thursday, August 15, 2019 9:01 PM

Thanks Mel, very nice and thorough discussion!  Gave me lots to investigate on ebay!

Thanks Randy, you're always very helpful and thorough in your commentary! Both you have given great suggestions!  This is why I come to the forums!

Best,

Rick

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Posted by IDRick on Friday, August 16, 2019 10:08 AM

Couple quick questions:

Can the arduino drive two servos from one connection point to the controller with a y-servo extender?   Tam Valley uses this approach: 

 http://www.tamvalleydepot.com/support/crossovers.html

Does this increase the number of servos that can be controlled?  Say I buy a Uno and have five turnouts plus a crossover.  As I understand it, a Uno can control six servos but may be able to control seven if the y-servo connector can be used.  I will obviously be a lone operator so will only be switching one or two turnouts at a time.

The tam valley fascia controls + mounts are kinda expensive but I like the easy installation and protection from inadvertant switching.  Can they be used with an arduino controller and correctly light showing switch orientation?

For this benchtop test with a very basic switching layout, I'll probably just purchase servo extender cables from ebay as they are inexpensive and free shipping.  I agree with Mel I could save money by making my own but for this test premade are perhaps a better use of my time.

The Iowa Scale Engineering mounts are very reasonably priced and have some mounting flexibility if adjustments are needed.  Hat tip to Randy!

Lots of good stuff about arduinos on youtube.  Randy, thanks for the tip on Geoff B., he's an excellent resource.

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Posted by RR_Mel on Friday, August 16, 2019 10:22 AM

Rick
 
Yes the Arduino can drive more than one in parallel from a single port or multiple ports from the programming.  I have driven four from a single port on my bench testing.
 
I thought I would post a picture of my bench power supply.
 
 
The Arduino on the right is a 20 port 500ma Random Lighting Controller.
 
Top are the Digital 0 to 20 voltmeters, under the meters are a pair of DC to DC converters attached to a 12 volt 15 amp switching power supply.
 
Costs:
 
UNO with the Mel high current driver expansion board
         UNO - $4.53 free S&H
         Expansion board - $2.20 free S&H
         Seven channel 500ma driver chips $1.50 free S&H
 
Digital Meters - $2.47 each free S&H = $4.94
 
DC to DC converters - $3.58 each free S&H = $7.16
 
12 volt 15 amp switching power supply - $19.89 free S&H (USA)
 
Power Supply Total - $32   Not too bad for 5VDC at up to 8 amps and 8.6VDC at up to 8 amps,  The regulated DC to DC converters can go as high as 12 amps with fan cooling.
 
The DC to DC converters are set to 5 volts for my Arduinos & servos and 8.6 volts for the 12 GOW incandescent bulbs.  I use reduced voltage for all of my lighting, 1) the GOW bulbs look much more realistic operating at 70% voltage, 2) it greatly improves bulb life, I haven’t had to replace a bulb in over 20 years.
 
Here are a couple of early on pictures of the DC to DC converters as installed.
 
 
 
All three of the DC to DC converters are power by a similar 12 volt switching power supply with 30 amp capacity (same physical size as the 15 amp) mounted externally on the side of the control panel.
 
 
Mel
 
 
My Model Railroad   
 
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I'm beginning to realize that aging is not for wimps.
 
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Posted by RR_Mel on Friday, August 16, 2019 11:15 AM

Rick
 
I thought I might add something that could make a difference on driving more than one servo in parallel.  The Tower SG90 servos are super cheap so micro positioning could be a problem.  The individual servo accuracy isn’t precession from one servo to another, better than ballpark but far from micro positioning.
 
The specs on the SG90 say 180° rotation, only one out ten would do 180° the rest were from 160° up.  Never the less for $1.49 they work very good.
 
I had similar experience with the 7g micro servos at $1
 
 
 
Mel
 
 
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I'm beginning to realize that aging is not for wimps.
 
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Posted by rrinker on Friday, August 16, 2019 12:02 PM

 And that's perfectly OK at least for controlling turnouts as 180 degree rotation is generally not needed. 

 As far as driving multiples - here's the trick. A servo has 3 wires going to it, one is ground, one is power, and the third one is the signal line that controls the position based on the width of the pulses that coem over this control line. The 'power' used to turn the motor in the servo comes over the two other wires in the cable. Arduinos have a limit to how much current can be drawn from any one pin before the chip is damaged, however the signal line to the servo draws very little power. So you can connect the signal line of multiple servos to a single Ardunio output without harming anything.

 Most if not all of the Tam Valley controllers us PIC microcontrollers, but at the interface level (ie, where you plug things in), that makes no real difference. Hooking multiple control lines to one output is exactly what you are doing when you hook 2 servos together with a wye cable.

 No microcontroller can source enough current to actually turn the motor of the servo, those lines connect directly to the power input or the voltage regulator for the entire controller circuit. So while a moving servo might draw halg an amp or more depending ont he load, it's only putting a very minuscule load on the controller to get the position signal on the control line.

                               --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by IDRick on Friday, August 16, 2019 12:34 PM

Randy, excellent information!  Can you give me a recommendation on power supply for the UNO and Mega?  Can a wall wart with 1 to 2 amp output (9 volts) be used? 

Thanks for clarifying on joining two servos!  What about the fascia mounts and lights, how are they connected to an arduino and will show correct turnout location?

Mel, nice set up!  Very obvious that you love electronics and are very talented in using it in our hobby!  I'm at the barely crawling stage of understanding so be very basic in my test setup.  Thanks for sharing!

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Posted by RR_Mel on Friday, August 16, 2019 1:16 PM

Randy
 
I’m glad you brought that up, I constantly forget the little things that I take for granted everyone knows.
 
 
Rick
 
I don’t use the 7 to 12 volt input to the Arduinos.  I bypass the Arduino internal regulator, another source of internal heat.  I power all of my Arduinos from the 5 volt pin on the board from my 5 volt DC to DC converters.  You want to avoid heat around solid state stuff as much as possible.
 
I power all my lighting and servos from my power supplies never from an Arduino.  Always use the Arduino ports for control only.  My lighting controller switching only requires 1 to 2ma from the Arduino ports.  The switched Arduino control output goes to a seven channel high current chip, a 1ma low from the Arduino switches the 500ma output of the chip.
 
I power the servos (RED & Brown) direct from a 5VDC high current source, in my case the 8 amp DC to DC converters.  The SG90 control current (Orange) is 3ma so I didn’t have a problem driving four servos from a single port, four servos at 3ma = 12 ma.  If you stall a SG90 the current is over 200ma on the Red wire.
 
I would suggest you buy a servo tester for experimenting and testing, much easier as well as safely testing your servos.  I bought a Turnigy Servo Tester.
 
 
It will allow you to drive four servos in parallel for testing.
 
 
Mel
 
 
My Model Railroad   
 
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I'm beginning to realize that aging is not for wimps.
 
 
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Posted by rrinker on Friday, August 16, 2019 2:28 PM

 The regulator built in to the Arduino isn't really capable of driving more than 1 or maybe 2 servos. A 1 or 2 amp 5V power supply (the little bricks used for phone or tablets are a good option - you just have to cut the phone end connector off to expose the wire). For driving 6 or more servos, you'll want a more powerful power supply.

                         --Randy


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Posted by IDRick on Friday, August 16, 2019 4:02 PM

Mel, very thorough description of your power supply set up!  Didn't fully appreciate the need for that size at first, now I understand your need for switching power supply plus DC/DC reducing transformers. 

For me, I think the best bet is to start small.  For my test switching layout, I will use caboose hobby ground throws on single turnouts.  For the one or two crossovers, I would use an Uno, 2 or 4 servos, 1 or 2 wye cords, Tam Valley fascia mounts + LED, and a 2 amp 5 volt power supply.  Only one crossover would be used at a time so should be sufficient power.

The costs for a higher amperage switching power supply and a DC/DC reducing transformer really need to be included when comparing arduino versus tortoise control of turnouts.  Plus, one needs to properly size power supply and transformer to meet future needs rather than planning an initial test setup.

My main use for considering arduino is to operate crossovers.  I prefer to use caboose hobbies ground throws for industry, yard track, and single turnouts.  Looks like optimizing use crossovers is a great idea to minimize cost, just like for the railroads!  It's too early for me to make those decisions.  Thanks for your help Mel and Randy!

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Posted by RR_Mel on Friday, August 16, 2019 4:33 PM

 
When you aveage out the cost of using servos the cost per turnout drops fast as you add more turnouts.  When (if) I get all 21 turnouts done the cost per turnout will cost less than $6 each including the Arduino and Power Supply cost.
 
In my case I really don't need to add in the power supply costs as I had already built up my accessory power supply to 30 amps for lighting and automation goodies.
 
I'm only changing out the close to 30 year old Atlas Under Table Switch Machines as they crap out and I turned 82 two weeks ago so . . . .
 
I just did a recheck of the stall current on a couple of 7g servos and at stall they draw 435ma at 5 volts.  Using the Turnigy Tester in Auto Mode a single 7g servo draws 16.2 to 18.7 ma with no load.  I plugged four 7g servos into the tester to check the amount of rotation and three are close at about 120° and the fourth has about 160°.  Not very good quality control but all four have gobs of power, for 99¢ each not too bad for model railroading.
 
I use a pair of 7g servos to open and close the doors on each stall of my roundhouse.  I have them paralleled so I invert the mounting of one to operate both doors from one Arduino port.  It was easier to use two servos rather come up with a mechanical way control both doors from one servo.  The movement of the doors on the Korber HO roundhouse have 100° swing so the 120° max 7g servos work great.  The 7g servos are about ¾ smaller than the SG90 servos.
 
Mel
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 

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