Selectable Voltage Sensing relay 0-18V AC

[jensenjosht]

I was wondering if I could get some help on trying to electrically solve this idea I had. I was wondering what the best way would be to set the maximum voltage limit from a variable AC transformer so that it could never exceed a selectable predetermined voltage and if it did, would just force the output voltage down to the predetermined threshold.

The variable AC input would be a from a Lionel CW-80 transformer that would power a conventional train set. The idea was to have a system so that you could never drive the train at a voltage higher than what I would select to prevent the train from being driven too fast and having the train derail violently. This was going to be used at Christmas event in November where kids will be able to operate the train and where a system described above would be cool.

I’ve done some preliminary research in to using a Varriac, voltage sensing relay, and a op amp comparing circuit, but I felt slightly confused, conflicted and overwhelmed that I wanted to put the idea in front of more possibly experienced minds.

0-18v ac 60hz, 80w for electrical loads. I can post some manuals for the transformer.

 

[marconi]

Good evening from London. I am not a railway modeller nor am I familiar with the latest technology. The last time I played with a model railway was in the late 60s with this set using a 12V direct current rheostat controller with current limiting using a small 12Volt filament lamp.


I have done a little research on the Lionel controller you mentioned and your requirement to limit its output. Since at this stage I do not know your level of electrical knowledge I will simply say for now that the Lionel CW80 uses a so-called chopped sine wave (hence the CW in CW80) to control the power supplied to the loco's motor. A variac may work but would need to be tested first to confirm that because the output sinewave may not be reliant on the input mains sine wave ie the output sine wave might be generated electronically. But I would advise against it because the much simpler and effective solution - to be confirmed - is to limit the arc over which the LionelCW80 throttle knob moves - a mechanical solution.

You (and me) need to know what type of motor is in the locomotive and what electronics are wrapped around it before even considering an electronic solution. At this stage I am assuming an ac universal motor with split field.

Vintage Hornby / Meccano 00 Gauge Power Control Unit Type A2 - Untested | eBay - https://www.ebay.co.uk/itm/124576773754?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=124576773754&targetid=293946777986&device=c&mktype=pla&googleloc=9045003&poi=&campaignid=17116423086&mkgroupid=134652533165&rlsatarget=pla-293946777986&abcId=9300856&merchantid=531357731&gclid=Cj0KCQjwnP-ZBhDiARIsAH3FSRffmjadPwlCendM_ZVu0IRE7_gBgpF1mb7jSGUtNSH6QxN2kCRW3r8aAga2EALw_wcB

 

[marconi]

R-fur has contacted me and helpfully pointed to the MERG - the Model Electronics Railway Group UK. We suggest you post your query on this site:

Model Electronics Railway Group - https://www.merg.org.uk/

 

[jensenjosht]

Good evening from London. I am not a railway modeller nor am I familiar with the latest technology. The last time I played with a model railway was in the late 60s with this set using a 12V direct current rheostat controller with current limiting using a small 12Volt filament lamp.

View attachment 102310
I have done a little research on the Lionel controller you mentioned and your requirement to limit its output. Since at this stage I do not know your level of electrical knowledge I will simply say for now that the Lionel CW80 uses a so-called chopped sine wave (hence the CW in CW80) to control the power supplied to the loco's motor. A variac may work but would need to be tested first to confirm that because the output sinewave may not be reliant on the input mains sine wave ie the output sine wave might be generated electronically. But I would advise against it because the much simpler and effective solution - to be confirmed - is to limit the arc over which the LionelCW80 throttle knob moves - a mechanical solution.

You (and me) need to know what type of motor is in the locomotive and what electronics are wrapped around it before even considering an electronic solution. At this stage I am assuming an ac universal motor with split field.

Vintage Hornby / Meccano 00 Gauge Power Control Unit Type A2 - Untested | eBay - https://www.ebay.co.uk/itm/124576773754?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=124576773754&targetid=293946777986&device=c&mktype=pla&googleloc=9045003&poi=&campaignid=17116423086&mkgroupid=134652533165&rlsatarget=pla-293946777986&abcId=9300856&merchantid=531357731&gclid=Cj0KCQjwnP-ZBhDiARIsAH3FSRffmjadPwlCendM_ZVu0IRE7_gBgpF1mb7jSGUtNSH6QxN2kCRW3r8aAga2EALw_wcB

The trains I’m running are from the from the early to mid 2000’s. Most Lionel trains us a universal motor meaning that they can use AC or DC. However, the whistle and bell use DC offset voltage to trigger it when the respective buttons are pressed. So on DC the whistle/bell would constantly be activated while voltage is applied(A Classic Whistle and Sneezes Moment from TTTE) on DC unless it’s rewired to not do that. If I can I’d like to avoid re-wiring unless absolutely necessary. As you can imagine, with kids on the Autism spectrum attending, I want to avoid having the whistle constantly on while the train is in motion unless asked for.

Attached are the sets I plan on using. Both from the same era both classic AC control.

 

[jensenjosht]

R-fur has contacted me and helpfully pointed to the MERG - the Model Electronics Railway Group UK. We suggest you post your query on this site:

Model Electronics Railway Group - https://www.merg.org.uk/

Don’t mind joining or posting but the problem is that I’m USA based in Iowa. I wouldn’t mind joining and paying the membership but Im not too familiar or comfortable with it at the moment.

 

[marconi]

Thank you. I will study what you have sent me. I think - cannot be sure just now - that the Lionel CW80 outputs a waveform as in my electrical art below to drive an ac universal motor. Forward and reverse is achieved by full wave rectification of the chopped sine wave (CSW) and then applying this waveform to the track with normal or swapped polarity - the second and third green waveforms. The frequency and peak voltage never changes. Speed control is by varying the delay before the sine wave is applied to the output the delay T being controlled by the throttle position. I do not know yet if the frequency of the output waveform is the same as the mains input sine wave which in the USA is 60Hertz. A variac on the mains input side may be a solution because it might reduce the amplitude of the output sine wave. A variac may not work though if the Lionel CW80 has voltage regulation on the output. Do you have a variac, an ac voltmeter and a couple of low wattage 12V filament lamps (not LED lamps)?

I have to ask in order to guide how I write to you - what is your level of understanding of electrical science please?

 

[marconi]

lionel CW 80 watt transformer - https://ogrforum.ogaugerr.com/topic/lionel-cw-80-watt-transformer

Just did some Googling to see if I could buy in uk a lionel cw80 or one that is defective in some way to bench test. The cw80 does not get good reviews. It seems one has to be very careful about which older motors it drives. Why have you decided on the lionel cw80? Did it arrive with the polar express? I will look up what transformer the polar express requires. Do you have the polar express already in which case what transformers does it say to use please?

 

[marconi]

Don’t mind joining or posting but the problem is that I’m USA based in Iowa. I wouldn’t mind joining and paying the membership but Im not too familiar or comfortable with it at the moment.

I understand. I will see how much I can help you then but please be patient with me as I learn.

PS: Just so I can place you in the world and my interest would you tell me which town or city you live in? Do not post your address or other details about yourself.

 

[marconi]

I have managed to find some pictures of the inside of a cw80 and a circuit diagram for it plus the China website for the 120V-18V step down transformer an EI76-009. What is the vintage of your cw80 because I have read the it has been updated though I doubt the circuitry has changed much. I need more time to ponder it but your variac idea may well work. We can do a safe trial to confirm this.

 

[marconi]

I just need to know now if you have a variac, ac voltmeter and a couple of 12V filament lamps or one 24V filament lamp to act as a temporary load instead of the locomotive. Then I will describe a test to you to see if your idea works.

Do your locomotives have an e-unit inside them or do they only ever move forwards?

 

[jensenjosht]

lionel CW 80 watt transformer - https://ogrforum.ogaugerr.com/topic/lionel-cw-80-watt-transformer

Just did some Googling to see if I could buy in uk a lionel cw80 or one that is defective in some way to bench test. The cw80 does not get good reviews. It seems one has to be very careful about which older motors it drives. Why have you decided on the lionel cw80? Did it arrive with the polar express? I will look up what transformer the polar express requires. Do you have the polar express already in which case what transformers does it say to use please?

I have managed to find some pictures of the inside of a cw80 and a circuit diagram for it plus the China website for the 120V-18V step down transformer an EI76-009. What is the vintage of your cw80 because I have read the it has been updated though I doubt the circuitry has changed much. I need more time to ponder it but your variac idea may well work. We can do a safe trial to confirm this.

That’s fine. I only was using the CW80 because that’s what came with it. Used it for years and never had any trouble with it. Like I said the idea was to do a pass through system outside of the transformer on the output terminals. I know enough electricity to get my self in and out of trouble to varying degrees of success.

 

[marconi]

I will draw you a diagram tomorrow showing how to test your idea.

 

[jensenjosht]

I just need to know now if you have a variac, ac voltmeter and a couple of 12V filament lamps or one 24V filament lamp to act as a temporary load instead of the locomotive. Then I will describe a test to you to see if your idea works.

Do your locomotives have an e-unit inside them or do they only ever move forwards?

They can run forward and back. I’d presume they would. They’re old but not that ancient.

 

[jensenjosht]

I understand. I will see how much I can help you then but please be patient with me as I learn.

PS: Just so I can place you in the world and my interest would you tell me which town or city you live in? Do not post your address or other details about yourself.

Cedar Falls, Iowa. North eastern portion of the state. I’m not too worried yet.

 

[marconi]

Here is a simple diagram for the test. The single 24V lamp (or two similar 12V lamps in series) are connected to the traction terminals. Plug the Lionel(L) into the Variac (V) and ensure the Variac is set to output 120V. Now plug the Variac into the mains. The lamp(s) should illuminate.

Now reduce the Variac output voltage by a small amount and you should see the lamp(s) dim. If you reduce the Variac voltage by too much the Lionel will shut down because its internal 5V dc voltage regulator will turn off which in turn will turn off the electronics.

There is only a limited range over which you will be able to reduce the traction peak voltage. The Lionel's internal transformer outputs about 20Vac which after rectification is about 18Vdc. The minimum voltage at the input to the linear 5V dc voltage regulator is 7.2V - it is an LM78L05 if that means anything to you.. So if you use the Variac to reduce the 120V it will pro rata reduce the 20Vac and thence the 18Vdc until 7.2Vdc is reached and the Lionel will shut down. I do not advise you make such a large reduction. You will not need a big reduction to set an upper limit on the train's speed along the track because the power of the loco motor is roughly a function of the voltage squared.

Once we have demonstrated the V-L combination does indeed dim the lamp(s) we can move on to providing power to the locomotive.

PS: The maximum current from the Lionel is about 5A so the total wattage of the lamp(s) must less than 5 x 18 = 90W.

 

[marconi]

Cedar Falls, Iowa. North eastern portion of the state. I’m not too worried yet.

I will look this up in my world atlas

 

[marconi]

Cedar Falls, Iowa. North eastern portion of the state. I’m not too worried yet.

I live in London on its East side on the North side of the River Thames.

 

[jensenjosht]

Thank you. I will study what you have sent me. I think - cannot be sure just now - that the Lionel CW80 outputs a waveform as in my electrical art below to drive an ac universal motor. Forward and reverse is achieved by full wave rectification of the chopped sine wave (CSW) and then applying this waveform to the track with normal or swapped polarity - the second and third green waveforms. The frequency and peak voltage never changes. Speed control is by varying the delay before the sine wave is applied to the output the delay T being controlled by the throttle position. I do not know yet if the frequency of the output waveform is the same as the mains input sine wave which in the USA is 60Hertz. A variac on the mains input side may be a solution because it might reduce the amplitude of the output sine wave. A variac may not work though if the Lionel CW80 has voltage regulation on the output. Do you have a variac, an ac voltmeter and a couple of low wattage 12V filament lamps (not LED lamps)?

I have to ask in order to guide how I write to you - what is your level of understanding of electrical science please?

I have some bulbs that are 12v. I need to purchase a variac.

 

[jensenjosht]

Here is a simple diagram for the test. The single 24V lamp (or two similar 12V lamps in series) are connected to the traction terminals. Plug the Lionel(L) into the Variac (V) and ensure the Variac is set to output 120V. Now plug the Variac into the mains. The lamp(s) should illuminate.

Now reduce the Variac output voltage by a small amount and you should see the lamp(s) dim. If you reduce the Variac voltage by too much the Lionel will shut down because its internal 5V dc voltage regulator will turn off which in turn will turn off the electronics.

There is only a limited range over which you will be able to reduce the traction peak voltage. The Lionel's internal transformer outputs about 20Vac which after rectification is about 18Vdc. The minimum voltage at the input to the linear 5V dc voltage regulator is 7.2V - it is an LM78L05 if that means anything to you.. So if you use the Variac to reduce the 120V it will pro rata reduce the 20Vac and thence the 18Vdc until 7.2Vdc is reached and the Lionel will shut down. I do not advise you make such a large reduction. You will not need a big reduction to set an upper limit on the train's speed along the track because the power of the loco motor is roughly a function of the voltage squared.

Once we have demonstrated the V-L combination does indeed dim the lamp(s) we can move on to providing power to the locomotive.

PS: The maximum current from the Lionel is about 5A so the total wattage of the lamp(s) must less than 5 x 18 = 90W.

Looks good but it might be a bit. I’ve got to get a varriac.

 

[marconi]

Looks good but it might be a bit. I’ve got to get a varriac.

Do ask me for further explanations if you are not sure about something.