Point motor advice

[rreckless]

I'm after some advice on point motors and suchlike. I'm swaying between servo and SEEP point motors, mostly because I don't fully understand everything about controlling servo points.

I've looked at the systems the MegaPointControllers sell and they look great but they're pricey. Is there a cheaper way of controlling 31 servo motors? I've seen the thread about "Servos and lights" by aleopardstail, but don't understand how it's controlled through arduino.

Is anyone able to assist me and increase my understanding?

[rreckless]

Also if I go down the servo route, is there a way of reversing the polarity where needed as there is with SEEP PM1 motors?

[centenary]

I'm after some advice on point motors and suchlike. I'm swaying between servo and SEEP point motors, mostly because I don't fully understand everything about controlling servo points.

I've looked at the systems the MegaPointControllers sell and they look great but they're pricey. Is there a cheaper way of controlling 31 servo motors? I've seen the thread about "Servos and lights" by aleopardstail, but don't understand how it's controlled through arduino.

Is anyone able to assist me and increase my understanding?

I use DCC Concepts IP Analogs for point motors and MegaPointControllers will be used to control them, although I havent wired the IP As to the boards yet (next job!).

Personally, Id go IP As every time rather than Seep or even IP Digitals. Im currently using the 2nd switch in the IP As to isolate power to sidings when the point is against the relevant road and, turning off power approximately a loco length from the point when it is against that line (interlocking?).

I would have used DCC Concepts own boards to control the IP As but, they stopped making the Alpha Switch Analog board and now only sell the digital version. Richard at DCC Concepts told me he did have some of the Analog boards left in stock but my worry was buy them and if one went faulty in the future, Id be stuck with no more available.

You can control the IP As via the DCC Concepts digital boards but you have to buy an expensive interface for every 8 IP As you have. To save money, you can still just use analog 12v power and the special switches from DCC Concepts but these are expensive too at 25 quid for 6 switches and 2 leds per switch!

Dave at MPC had just brought out his System 2 Air. I think it's an excellent system, very versatile and configurable plus makes it easy to control as many switch machines as you want via 1 switch via the virtual port set up.

Dave is very reluctant to confirm DCC Concepts exist and tried to steer me away from the IP As and use Tortoise instead. Consequently, Dave will not make a System 2 board for IP Digitals although he did for his now 'Classic' system

Id already committed to the IP As and beside, I think they are better than Tortoise (imho). The IP As and Tortoise are both stall motors and when I tested the IP As with the S2 boards, there was no problem.

Unfortunately, Dave has jacked his prices considerably since he release the S2 boards a few years ago. I was fortunate and bought my last set of boards before his last price increase. I would have to seriously consider buying the S2 System now given the prices. The boards for the Seep motors are, well, I think unreasonable for the 'starter system' but that's just my opinion.

I also costed the S2 system using cheap servos and relays compared to the IP As. There wasnt much difference in price between the 2 and I considered all that I wanted in the IP As outweighed the small cost saving of servos + relays etc.

If you do want any more info about MPC S2, drop me a pm.

[centenary]

Also if I go down the servo route, is there a way of reversing the polarity where needed as there is with SEEP PM1 motors?

If you used the MPC system, the servo boards and required relays do the frog switching for you.

There are other manufacturers who provide the same functionality but I didnt really follow them up.

[Flashbang]

I'm after some advice on point motors and suchlike. I'm swaying between servo and SEEP point motors, mostly because I don't fully understand everything about controlling servo points.

I've looked at the systems the MegaPointControllers sell and they look great but they're pricey. Is there a cheaper way of controlling 31 servo motors? I've seen the thread about "Servos and lights" by aleopardstail, but don't understand how it's controlled through arduino.

Is anyone able to assist me and increase my understanding?

Have a look at MERG (Model Electronic Railway Group) https://www.merg.org.uk/. They sell (to members only) several types of servo control boards and some that have a built-in relay for frog polarity changing or switching other circuits, such as a colour light signal. You do have to assemble the kits, so the use of a soldering iron is needed, but they go together easily and there is a huge amount of support if needed via the MERG forum. Example Kit 77S is a single servo drive board at £4.64 while with added relay Kit 77R is just £6.34 or 5 x 77RM pack for £28.37 (£5.67 each PCB). A four-servo but non relay fitted module is £5.54.

Usually, servo boards just need a 12 volt DC smooth and regulated power supply and each servo is operated via a simple On/Off toggle switch, connected to the controlling boards terminals. The speed of throw and the amount of throw are adjustable, and they give a much smother operation than any solenoid can. 9g Servos themselves cost around £1.50 or more and mounting brackets are available too. Amazon servos these may not be the best servos, but at £1.50 each if one should ever fail then its not that expensive to replace it! Small size wire between the switch and the PCB is all that's needed, unlike solenoids which usually require a larger size of wire due to their momentary current draw - often around a momentary 4.0Amp flows.
Breaking it down to per point end and using MERG kit 77RM 5 pack £5.67. Servo £1.50 and MERG mounting kit pack of 6 each is £0.75 per bracket. Total per point £7.92.

[aleopardstail]

Hi, the arduino method isn't too bad - if you don't mind a bit of coding, for a "plug and go" the megapoints system and the MERG systems apparently are pretty good.

the arduino way is basically:
- an arduino of some sort, which one depends on how you want to control things - I use ESP32 and control over wireless via MQTT. I have previously used a basic arduino Nano and used the C/MRI system from a PC - you could also use push buttons to tell it which ones to set or to toggle - its a thing in itself getting info in - it does however make one button route selection quite simple.
- a PCA9685 board, this can drive 16 servos, you can have multiple of these things - you will need a suitable 5V power supply, I'd use a different one for the servos than for the arduino as you can get power and voltage dips
the servos plug into the board directly, you now have full control over them in software - the modification I wrote about is removing a resistor and adding one elsewhere, this makes damned sure the buggers don't move when you first power on
- you then have software, I wrote my own but there is a library by Adafruit that works nicely. essentially you need to then fiddle with the servos to find what value to use for the closed and the open position for the points and when you get the right input, set the output.
- for Frog control there are two options, switches mounted to the servos, the MERG servo mounts are designed for this, or using a relay controlled by the arduino, commercial relay boards work just fine and are what I use, there are various ways to drive these in code

Servos have the advantage of being cheap, and the disadvantage of being fiddly. SEEP ones can be driven via probe & stud with a capacity discharge unit which is very easy to set up - lots of wires though

[rreckless]

Hi, the arduino method isn't too bad - if you don't mind a bit of coding, for a "plug and go" the megapoints system and the MERG systems apparently are pretty good.

the arduino way is basically:
- an arduino of some sort, which one depends on how you want to control things - I use ESP32 and control over wireless via MQTT. I have previously used a basic arduino Nano and used the C/MRI system from a PC - you could also use push buttons to tell it which ones to set or to toggle - its a thing in itself getting info in - it does however make one button route selection quite simple.
- a PCA9685 board, this can drive 16 servos, you can have multiple of these things - you will need a suitable 5V power supply, I'd use a different one for the servos than for the arduino as you can get power and voltage dips
the servos plug into the board directly, you now have full control over them in software - the modification I wrote about is removing a resistor and adding one elsewhere, this makes damned sure the buggers don't move when you first power on
- you then have software, I wrote my own but there is a library by Adafruit that works nicely. essentially you need to then fiddle with the servos to find what value to use for the closed and the open position for the points and when you get the right input, set the output.
- for Frog control there are two options, switches mounted to the servos, the MERG servo mounts are designed for this, or using a relay controlled by the arduino, commercial relay boards work just fine and are what I use, there are various ways to drive these in code

Servos have the advantage of being cheap, and the disadvantage of being fiddly. SEEP ones can be driven via probe & stud with a capacity discharge unit which is very easy to set up - lots of wires though

Your arduino method I think is what I want. I'm a software engineer by trade, so coding doesn't concern me. I have a Raspberry Pi that I think will be able to replace the arduino as the control for the boards.

I need to do some more research in to controlling servos this way, but this is definitely what I want to do. Thanks!

[aleopardstail]

the Pi should do fine as you don't want to drive the servos directly, get hold of a PCA9685 16 channel PWM board and a few servos. there are libraries for the Arduino you can crib from to drive them but frankly the datasheet has what you need.

you may however find it easier to have the Pi talk to a proper micro controller to do that stuff, then you can just send it "point 1, throw it please if you would be so kind" and get back "tis done sir". the Pi Pico is pretty good

put it like this, if I can do it, anyone can

[rreckless]

the Pi should do fine as you don't want to drive the servos directly, get hold of a PCA9685 16 channel PWM board and a few servos. there are libraries for the Arduino you can crib from to drive them but frankly the datasheet has what you need.

you may however find it easier to have the Pi talk to a proper micro controller to do that stuff, then you can just send it "point 1, throw it please if you would be so kind" and get back "tis done sir". the Pi Pico is pretty good

put it like this, if I can do it, anyone can

I've ordered the PCA9685 boards, servos and ESP32 board. Should arrive tomorrow, then it's time to learn

[rreckless]

Do you have a recommendation for power supply for the PCA boards and ESP32?

[aleopardstail]

Do you have a recommendation for power supply for the PCA boards and ESP32?

currently I'm using a 5V 2A wall wart for the PCA board to drive the servos, I have a separate 5v supply driving the ESP32 (common ground) - I was getting a few issues with power surges causing the ESP32 to reset - a more beefy supply and a few smoothing capacitors for both the servos and the ESP32 would see both fine

note the servos can have remarkably high stall currents (enough to melt them). anything 2A-5A at 5A will do fine, depends how many you want - but if set up right the switch rails only need to touch so shouldn't be any significant load.

the 5V 2A supply I have is currently driving 10 Servos and will soon have 12 on it, plus associated frog relays and seems to be coping fine

[rreckless]

I have my 1st servo controlled by Raspberry Pi.

Been a while since I did Python coding, but I'm already thinking about how I can set up routines etc

[aleopardstail]

I have my 1st servo controlled by Raspberry Pi.

Been a while since I did Python coding, but I'm already thinking about how I can set up routines etc

if you have a can a lovely little test project is a "cat exerciser", two servos, a small speaker than can play simple tones for a beep and boop sound track

then a laser pointer and code to make random adjustments

[aleopardstail]

Never used python, just C/C++ here, something I found pretty useful was a class object to manage the thing, then a loop function you call with an elapsed time from the last time it was called - makes it reasonably simple to have a constant angular velocity or a constant time period to go between two positions. slow movement is wonderfully quiet too

I have an object to manage the PCA9685 and another for an individual servo, end up with an array to loop through.

likely have a video coming up on the actual software set up I use

[rreckless]

Never used python, just C/C++ here, something I found pretty useful was a class object to manage the thing, then a loop function you call with an elapsed time from the last time it was called - makes it reasonably simple to have a constant angular velocity or a constant time period to go between two positions. slow movement is wonderfully quiet too

I have an object to manage the PCA9685 and another for an individual servo, end up with an array to loop through.

likely have a video coming up on the actual software set up I use

I'll be watching that video!