TheRailwire
General Discussion => DCC / Electronics => Topic started by: jbonkowski on September 28, 2022, 11:56:47 PM
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I'm trying to update some of the electronics on my club layout. We have several large yards that use diode matrices along with Tractronics Switchlock boards to control the Tortoise machines. Unfortunately, Tractronics is no longer in business.
Is there another product out there that performs the same function? There seem to be a few products out there for controlling Tortoise machines, but they seem designed around computer/DCC control. I need something that will throw the Tortoise based on two momentary contact button inputs, when either input is grounded, the Tortoise will go in one direction. I think Circuitron makes something for that, but it's ~$25 per Tortoise! Is there anything cheaper?
Does anybody even do a diode matrix anymore for yard ladders?
Jim
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You could use a latching relay - they are in the $5.00 to $6.00 range. I would add a snubber to make the relay contacts last longer. The tortoise is a pretty big inductive load.
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I think you could do this with latching relays as Rasputen suggests. I would use the DIP style that have higher-ohm coils (like 400 ohm or more) so that even if 10 or 20 of them fire at once when you push a pushbutton to select a route through your diode matrix, you don't have to worry about the relay coil current overloading your pushbuttons. There are DPDT latching relays like this for sale all the time on surplus electronics sites, eBay, etc, and many of them have the exact same pin-out, so if one ever fails and you mount them all in IC sockets, you can just unplug it and replace it. I have used latching relays like this for years.
If you want to keep using the non-mechanical solution (the Tractonics board or other)...
Any chance you can post close-up photos of the old Tractronics board so I can see what the circuit looks like?
If I understand this correctly, you push a pushbutton that is connected to your diode matrix, the various outputs of the diode matrix
power a bunch of those Tractronics boards, which "latch" even after you let go of the button, so they power a bunch of Tortoises to select the route through your yard ladder. Sounds like that Tractronics board is something like a simple flip-flop that could be reverse engineered easily enough if we could see the board close-up.
The Circuitron board you mentioned (I am guessing their "TC-3") probably does the same thing, but I notice in their instructions that they say that on power-up, it will randomly select one direction or the other, which would be bad. You want it to select NOTHING on power-up, so the switch machines all stay where they are.
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If somebody were to devine a new board that is functionally equivalent to the Tractonics or Circuitron board, but you had to buy the components yourself and solder them on, would that appeal to you? Once the circuit is devised, I can see from the Circuitron board that nothing on that board is very expensive. I'm sure all the parts could be had for 2 or 3 bucks at most - cheaper if you buy all the parts in lots of 20-30 if you are making a bunch of these. I'd be intrigued to see if I can duplicate the functionality of your board, and then you could solder them up yourself.
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This is an example I think
http://www.circuitous.ca/xSingleCoil4TrackLadder.html
(http://www.circuitous.ca/xSingleCoil4TrackLadder.GIF)
http://www.circuitous.ca/StallMatrix.html
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Another link to the Canadian site with the actual controller boards. I use about 30 of these boards to control some 80 Tortoises on my layout, and they have worked perfectly for 20 years.
http://www.circuitous.ca/556Stall08.html
John C.
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Another link to the Canadian site with the actual controller boards. I use about 30 of these boards to control some 80 Tortoises on my layout, and they have worked perfectly for 20 years.
http://www.circuitous.ca/556Stall08.html
John C.
The site that keeps on giving .. Not sure if he is still producing boards - but they seem simple enough to order some from a jobber
I think this might just be the ticket for the OPs question
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I wouldn't put the LED's in series with the tortoise as the one ciruitous.ca example (and the Circuitron instructions) shows. When the LED fails, you will lose function of your switch machine until you replace the LED.
When the voltage is reversed on a stalled motor, there is quite a large spike that will appear across the motor leads. I measured over 300 volts when reversing a 10 volt supply. There is an A/C component to this spike, which I think is caused by the piano wire throw rod that is unwinding itself as soon as the voltage changes. Thus you get about 5-6 fluctuations every time this event takes place.
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I acquired Tractronic's inventory years ago and still have some parts. I know we have diode matrix boards and I think we still have SwitchLocks if you want to keep with the same electronics.
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The thing I don't like about all of these circuits is that they all rely on a flip-flop that "assumes" one output state on power-up. So all your turnout ladders are going to move to that state when these things power on. One of Paisley's circuits on that page has a feedback from the spare contacts of the Tortoise to prevent this (the one that has "memory" to keep the last position). But I'm not really keen on that one either, because it only works for remembering the position of a sinlge turnout, not the selection of an entire ladder route through a diode matrix. The circuit really needs to be a tri-state output: Hi 1, Hi 2, or "neither", instead of just "hi" or "lo".
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Considering all this, the latching relay idea of Rasputen's is really starting to look like a winner here. Those things will say where you put them and the power-up won't move them.
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Rasputen: 300v kickback from the tortoise? Wow. Well, however the OP does this, you definitely want a simple snubber on all those Tortoises to keep them from destroying electronics or relay contacts. I'm surprised more of those Circuitron and other boards don't get damaged by this. But then, maybe they do and users don't know why.
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[attachimg=1]
Here is the ugliness you get back from the tortoise when you have it stalled in one direction and then reverse its polarity. I didn't bother with the really high frequency stuff as it is beyond what my portable scope could measure. The bottom of the screen is zero volts - if you look closely at the very lower right hand corner you can just see the trace is starting to stabilize at about +10 volts. If there were a simple inductor there, you would expect to see just one spike. Since the piano wire is mounted on the tortoise lever, it will start to wind the motor and gear train back towards the middle as soon as the voltage changes. I think this is what is causing all of the AC. I didn't take the time to clamp the tortoise arm in one position to prove this.
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Rasputen: we use all Tortises on my friend's layout. Totaling about couple of dozen. They are powered by a couple of 12V DC power supplies (large wall-warts), and we have LED indicators (2 reverse-connected LEDs in parallel) connected in series with the motor. If I recall the operating current in that circuit is about 5mA and stalled probably around 12mA. I don't remember exactly because we installed them about 20 years ago. Few are powered bu stationary decoders, while most are controlled by DPDT toggle switches. The layout has been operated regularly (usually one 2 hours operating session once par week, plus othr special events) and we have never had an LED get damaged.
Even if there is a high voltage inductive spike, I suspect that the reason the LEDs survive is because each LED protects its peer by clamping the voltage to around 2V (Vf for either LED while it is conducting). Wiring indicator LEDs into the motor circuit is actually widely recommended for Tortioses.
LEDs in general are damaged by either forward overcurrrent, or reverse voltage (excessive reverse voltage creates a destructive reverse current of the PN junction). I suspect that the current caused by the motor's high BEMF voltage is very low, and the forward-conducting LED can easily absorb it, clamping the voltage to very save 2V (thus protecting its reverse-wired peer LED).
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This is an example I think
http://www.circuitous.ca/xSingleCoil4TrackLadder.html
http://www.circuitous.ca/StallMatrix.html
John,
that schematic implies that the switch machines will only remain powered up for the duration of the throw (momentary push buttons). Stall switch machines should remain powered up after the throw is complete (that's why they are called "stall switch machines). Almost seems that this circuit is meant for the solenoid-type switch machines which throw one way or another depending on the polarity of the power fed into them. Like Kato Unitrak machines.
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Peteski, I have about 24 tortoises on my layout, which rarely gets run. I have had to change about 8 of the LEDs out, and it always seems to be the red one that fails. I made the mistake of using LEDs with integral leads and a plastic bezel, so they are very difficult to change. A local gentlemen is building a large S scale layout in his basement, and he is suffering from the same phenomenon, even though his layout is only 70% complete. My point is that when one of the LEDs fails, the tortoise will not function in both directions until you replace the LED, when they are wired in series.
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Peteski, I have about 24 tortoises on my layout, which rarely gets run. I have had to change about 8 of the LEDs out, and it always seems to be the red one that fails. I made the mistake of using LEDs with integral leads and a plastic bezel, so they are very difficult to change. A local gentlemen is building a large S scale layout in his basement, and he is suffering from the same phenomenon, even though his layout is only 70% complete. My point is that when one of the LEDs fails, the tortoise will not function in both directions until you replace the LED, when they are wired in series.
I've used some of the christmas light LEDs in the past .. left them in their holder -- one goes bad - pull it out
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Peteski, I have about 24 tortoises on my layout, which rarely gets run. I have had to change about 8 of the LEDs out, and it always seems to be the red one that fails. I made the mistake of using LEDs with integral leads and a plastic bezel, so they are very difficult to change. A local gentlemen is building a large S scale layout in his basement, and he is suffering from the same phenomenon, even though his layout is only 70% complete. My point is that when one of the LEDs fails, the tortoise will not function in both directions until you replace the LED, when they are wired in series.
Interesting. This is the first item I've heard of this problem. On my friend's layout we use standard green and yellow LEDs. Their chemistry is similar to standard red LEDs. By "standard" I mean the Gallium Arsenide material with Vf of 1.7 - 2.0V. Same as has been used since LEDs were first invented. If anything I would have expected the newer blue, true-green, or white (blue LED with yellow phosphor) LED getting damaged. Those are much more sensitive to voltage.
Are your LEDs wired the same way as my friend's? Are you using a 12VDC power?
(https://i.pinimg.com/736x/e1/8b/b4/e18bb441d8ca98aebf27f11b2b7470f5.jpg)
Also, if the LED failure model is an open circuit then the Tortoise would be able to still throw in one direction (not that this would be very useful). On the other hand, if the defective LED was shorted internally, the switch machine would still function normally (but the other working LED would not light up).
Like I mentioned, I'm not dismissing your claims of the problem, I'm just really surprised to hear about this problem, since if you do a Web search for Tortoise wiring diagrams, a majority show using LED indicators wired in series with the motor, and in the past I have never heard of the LEDs getting damaged (likely due to to the reasons I mentioned). If this is as serious of a problem as you say, I suppose adding a 0.1uF (500V ?!) in parallel with the motor terminals might flatten out those voltage spikes. Those caps are available dime a dozen, although 500V rated might be a bit harder to find. Maybe a 200V rated cap would suffice?
EDIT: This whole 300V thing just doesn't seem to add up to me. Was a x1 or x10 scope probe was used?
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Naïve question - does the physical size of the LED (not the plastic case, the gizmo inside) have any correlation to its robustness?
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Naïve question - does the physical size of the LED (not the plastic case, the gizmo inside) have any correlation to its robustness?
The die (the light emitting semiconductor chip) size of most standard LEDs is roughly the same (and very small). I would estimate it to around 0.010" - 0.015" square.
Only some of the high power white LEDs have larger dies, but that will not make them more robust as far as the reverse voltage is concerned (the most common cause for LED failures). Some LEDs (usually blue or white, since they are most fragile) have internal protection diode wired in reverse parallel with the LED die. That is for clamping the reverse voltage which could damage the LED.
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John,
that schematic implies that the switch machines will only remain powered up for the duration of the throw (momentary push buttons). Stall switch machines should remain powered up after the throw is complete (that's why they are called "stall switch machines). Almost seems that this circuit is meant for the solenoid-type switch machines which throw one way or another depending on the polarity of the power fed into them. Like Kato Unitrak machines.
look at the link right below it .
http://www.circuitous.ca/StallMatrix.html
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Interesting. This is the first item I've heard of this problem. On my friend's layout we use standard green and yellow LEDs. Their chemistry is similar to standard red LEDs. By "standard" I mean the Gallium Arsenide material with Vf of 1.7 - 2.0V. Same as has been used since LEDs were first invented. If anything I would have expected the newer blue, true-green, or white (blue LED with yellow phosphor) LED getting damaged. Those are much more sensitive to voltage.
Are your LEDs wired the same way as my friend's? Are you using a 12VDC power?
Also, if the LED failure model is an open circuit then the Tortoise would be able to still throw in one direction (not that this would be very useful). On the other hand, if the defective LED was shorted internally, the switch machine would still function normally (but the other working LED would not light up).
Like I mentioned, I'm not dismissing your claims of the problem, I'm just really surprised to hear about this problem, since if you do a Web search for Tortoise wiring diagrams, a majority show using LED indicators wired in series with the motor, and in the past I have never heard of the LEDs getting damaged (likely due to to the reasons I mentioned). If this is as serious of a problem as you say, I suppose adding a 0.1uF (500V ?!) in parallel with the motor terminals might flatten out those voltage spikes. Those caps are available dime a dozen, although 500V rated might be a bit harder to find. Maybe a 200V rated cap would suffice?
EDIT: This whole 300V thing just doesn't seem to add up to me. Was a x1 or x10 scope probe was used?
Yes, mine are connected like your diagram. On the S scale layout I referred to, I'm not sure how they are connected. The scope measurement I took was about 1 1/2 years ago so I don't remember the details. We were diagnosing noise issues with an Arduino, which is mounted close to the turnout controls on an HO layout. Adding high voltage caps did eliminate this problem.
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When I started building my layout about 15 years ago, I was using Minitronics bipolar red/green LEDs. A few of the red side burnt out within a few weeks. They were wired as in Pete's diagram. When they go out, the tortoise wouldn't work in some cases. Then I switched to ones I got from "MPJA.com" and they seam to last, although I've had a few of them burn out too, but the tortoise will still work. I also lowered the voltage to somewhere around 9 volts and haven't had any go out in quite some time. The Tortoise's are a lot quieter and slower too.
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look at the link right below it .
http://www.circuitous.ca/StallMatrix.html
(http://www.circuitous.ca/556Stall08Typical.GIF)
Ok, this is a totally different circuit than the schematic you posted. But this one is not set up for a diode matrix.
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(http://www.circuitous.ca/556Stall08Typical.GIF)
Ok, this is a totally different circuit than the schematic you posted. But this one is not set up for a diode matrix.
Peter . did you look at the entire page, or are you just interested in nit-picking every time I try to answer a question :x :x :x ? There are other examples in there that might help the OP!!!
I'm done with this!!!
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Peter . did you look at the entire page, or are you just interested in nit-picking every time I try to answer a question :x :x :x ? There are other examples in there that might help the OP!!!
I'm done with this!!!
No I didn't John. Guilty as charged. Sorry!
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No I didn't John. Guilty as charged. Sorry!
I apologize as well - I'm having a bad day
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I never upvote or downvote ANYTHING. But I upvoted those last two posts. Two people being nice.
50 quatloos!
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No I didn't John. Guilty as charged. Sorry!
I apologize as well - I'm having a bad day
Damn, I'm going to have to find another forum. TRW is getting too soft. :trollface:
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There haven't been any responses to my actual question about an off the shelf (OTS) product. I want to know what it will cost if I don't make my own from scratch.
The best thing I found, so far, is the NCE Button Board + Switch8-MK2. It has 8 pairs of normal (N) and reverse (R) inputs that will work with normally open (NO) pushbuttons, which means it will work with a diode matrix.
The downside is the price $30 + $70 = $100 to control 8 tortoises. This is actually a DCC solution, allowing throttle control of the turnouts as well, but that's not a requirement for us, or even something people will use.
So is there anything cheaper that does the job, besides building from scratch? It doesn't look like it, not anymore, anyway. Route control seems to be a DCC thing now, with the higher price tag that comes with it.[attachimg=1]
Jim
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I think you (and all the responses) answered your own question. There isn't anything off-the-shelf that is inexpensive that you can drop in there in place of your Tractronics boards.
Is copying the tractronics board and then soldering them up yourself absolutely out of the question?
That does require some work, but once you do it, you are set for life. You can make more any time you want, and you can replace bad ones yourself.
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Blank circuit boards and full kits for the Stall Motor drivers John pointed to earlier are available at http://www.circuitous.ca/556Stall08.html (http://www.circuitous.ca/556Stall08.html)
Diodes are available from electronic supplier for dime a dozen. A diode matrix (to control those stall motor drivers) can be wired ob a piece of blank perforated PB board (also readily available). Yes, it will take some work to get it all assembled, but you will have a reliable solution.
And Max does have a good idea. Maybe the Tractronics Switchlock circuit could be copied to make more of them.
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And Max does have a good idea. Maybe the Tractronics Switchlock circuit could be copied to make more of them.
Thanks, Pete. My thought is this. As I understand the situation, the OP has an installed base of a bunch of those boards working well already, and was originally looking for something that performed an "equivalent function". So if you *have* to make something, why not just make more of those? I bet those boards are simple enough that all we need is a close-up photo of each side (or one in hand that actually works would be awesome) to draw up the PCB plan (I'm a big fan of kicad), and then have them made. My experiences with Aisler is that for a small board like this, it should only cost about $4 each or less, and of course, if you go the route of a China maker, it will be literally less than dollar a board.
I will volunteer to draw up the PCB if somebody can get me a board or the photos.
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Thanks, Pete. My thought is this. As I understand the situation, the OP has an installed base of a bunch of those boards working well already, and was originally looking for something that performed an "equivalent function". So if you *have* to make something, why not just make more of those? I bet those boards are simple enough that all we need is a close-up photo of each side (or one in hand that actually works would be awesome) to draw up the PCB plan (I'm a big fan of kicad), and then have them made. My experiences with Aisler is that for a small board like this, it should only cost about $4 each or less, and of course, if you go the route of a China maker, it will be literally less than dollar a board.
I will volunteer to draw up the PCB if somebody can get me a board or the photos.
Like I said near the beginning of this thread, I have the actual Tractronics boards he is using if he wants more of the same..... :facepalm: Some of the boards for Tractronics products were printed in Mainline Modeler Magazine if you have those issues.
Should I use my invisibility for good or evil....
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Like I said near the beginning of this thread, I have the actual Tractronics boards he is using if he wants more of the same..... :facepalm: Some of the boards for Tractronics products were printed in Mainline Modeler Magazine if you have those issues.
Should I use my invisibility for good or evil....
I did see that haasmarc, sorry. I guess I assumed the OP wanted a solution that couldn't still one day "run out".
All it would really take is somebody to copy one of those boards into a new PCB layout, so they could be manufactured at will by anybody. I volunteered to do that, and I'd even make up one of them, to be sure it works. I know... electronics scares people. Honest folks, once you have the PCB layout file, you can upload it on a web page, and like magic, beautifully finished PCB boards show up at your door. You just have to be willing to solder some parts on them.
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Blank circuit boards and full kits for the Stall Motor drivers John pointed to earlier are available at http://www.circuitous.ca/556Stall08.html (http://www.circuitous.ca/556Stall08.html)
You are mistaken. See the circuitous.ca main page. He shut down the business in July.
Jim
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Thanks, Pete. My thought is this. As I understand the situation, the OP has an installed base of a bunch of those boards working well already, and was originally looking for something that performed an "equivalent function". So if you *have* to make something, why not just make more of those?
Actually, the Tractronics SwitchLock boards don't work THAT well. The ICs on them tend to die (which is why they are in sockets, to make them easy to replace). I don't know if this is due to the IC choice or if our layout is over-stressing them somehow. So I was hoping to try something different.
I wanted to see if there was any commercial product out there that does the job and isn't too expensive, and it appears there is not. I've now done a PCB drawing with my own solution to see if I can make something better. I still need to select the connectors/cabling.
While I'm at it, I'm going to do a diode matrix PCB, basically a "perfboard" but with some wiring already built in and places for connectors.
Jim
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You are mistaken. See the circuitous.ca main page. He shut down the business in July.
Jim
Here I go again - not reading things carefully enough.
Perfboard is ideal for home brew circuits like a diode matrix.
I would be curious to see a schematic of the SwitchLock board to see why those components blow up. I was under the impression that you were hoping to expend your current setup using the same circuitry already being used by you. Sorry that I misunderstood.
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I would be curious to see a schematic of the SwitchLock board to see why those components blow up.
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ME TOO! My thought exactly. Maybe that inductive kickback from the Tortoise motors is causing this.
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ME TOO! My thought exactly. Maybe that inductive kickback from the Tortoise motors is causing this.
[attachimg=1]
The Circuitron SwitchLock uses a flip-flop made from two NAND gates with the output fed to an op amp (x4 on the chip).
The op amp has a maximum rating of 570 mW and has 4 amps on one chip, so can drive four Tortoises at once. If each Tortoise is 16 mA at stall current and 12V, that's 768 mW. The instructions for the SwitchLock has a lot of detail, but they don't state their stall current assumption, so maybe they underestimated? One the other hand, they sold these for a long time, so the problem could easily be at my end.
I'm going to try a circuit made from LM556 timers. They can handle supply voltages up to 18V. I'm hoping they are harder to kill.
In the end, I'm really trying something else for the experience. It only costs a couple of dollars to replace all of the ICs on a SwitchLock, so the cheapest thing is just replace them when they fail (which is only one every couple of years).
Jim
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While it has been a while since I used LM324 Quad Op-amp in a circuit, or looked at its specs, going by my experience I would not have considered it for directly driving a DC motor (in a Tortoise). It is a low power analog amplifier, not designed as a motor driver.
I just did look up LM 324 specs, and while it can source 40mA and sink 20mA, it is not really best choice to drive an inductive load (a DC motor). I guess that might explain why it gets damaged. You might minimize the failures by adding a 0.1uF capacitor across the motor leads. That was mentioned earlier in this thread discussing the high voltage spikes. Also lowering the power supply voltage (thus reducing current), would likely help in reducing the failure rate of that chip, but will slow down the motor's speed.
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While it has been a while since I used LM324 Quad Op-amp in a circuit, or looked at its specs, going by my experience I would not have considered it for directly driving a DC motor (in a Tortoise). It is a low power analog amplifier, not designed as a motor driver.
The owner of the circuitous.ca website agrees, if you dig enough. Here is the last note he has about his stall motor control boards:
The 556 timer was chosen for these circuits because OPAMPS such as the LM324 or LM358 were found to be too unstable if the inputs are allowed to float and have a much lower current capacity.
Jim
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The owner of the circuitous.ca website agrees, if you dig enough. Here is the last note he has about his stall motor control boards:
The 556 timer was chosen for these circuits because OPAMPS such as the LM324 or LM358 were found to be too unstable if the inputs are allowed to float and have a much lower current capacity.
Jim
Good to know. Thanks Jim! I'm also a bit leery of using outputs of the 55X timers to directly drive the motor, but it seems that it has been done and it works. At least the timer's outputs are designed for full-on, full-off states.
I am also curious about those high voltage spikes Rasputen showed earlier. Next time I get my hands on a Tortoise (when my friend returns from an extended vacation) I'll have to connect my scope to it and see what surprises I discover.
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Golly... they are driving the turnout motor directly from the opamp ? For lack of a better word, ... EWWWWW.
I don't know how game you are, but it should be possible to just tack small driver transistors onto the outputs of the opamps, and then drive the motors off of those. Heck, little transistors are beyond cheap and could handle this with ease. They could be patched onto the board itself so there would be no mess.
Something like this:
(https://www.therailwire.net/forum/gallery/30/2667-111022204111.jpeg)
When Vin is +, the stall motor (Rsw) will have +11 ... GND across it. When Vin is -, it will have -11...GND across it.
Each transistor only has to dissipate about 20 mW, and the load on the opamp is something like only 200uA.
So if you drove 4 Tortoises, we're talking 80mW on a transistor that can easily dissipate double that, and still less than 1 mA load on the op amp.
Yes, it means 2 transistors and a resistor on each opamp output, but the cost is minimal.