Basic analogue controller for testing scratchbuilt locomotives

[Rhubarb Loop]

Hi guys,

 

I'm looking for a basic controller with no fancy feedback or the similar to build into a fixed locomotive testing rig / rolling road etc. I'm lead to believe that with no feedback it won't hide any tight spots. Any suggestions, perhaps something from a start set that can be picked up cheaply on eBay?

 

Cheers,

 

Alex

[bennyboy]

Try the controllers from the Farish/Bachmann trains sets, as they are surprisingly good for what you pay for them.

[AndyID]

If it's for a test-rig, an-old fashioned rheostat controller is your best bet. You will know if there are any tight spots because the voltage supplied to the motor will drop immediately and it will tend to stall.

 

If you can't get a controller like that you could get the same result with a DC supply, some nichrome wire, and a crocodile clip.

 

Andy

[DCB]

If it's for a test-rig, an-old fashioned rheostat controller is your best bet. You will know if there are any tight spots because the voltage supplied to the motor will drop immediately and it will tend to stall.

 

Andy

Good advice, if it will run smoothly on one of those it will run smoothly on anything.   

[Rhubarb Loop]

Ah, thanks guys! Armed with a couple of searchable terms I came across this basic controller design...

 

 

From this article -> http://www.instructables.com/id/Simple-controllers-for-DC-motors-inc-PWM-inertia/

 

I'm guessing that should do the trick nicely?

 

Presumably an analogue ammeter would be useful. Would one such as this http://uk.rs-online.com/web/p/analogue-panel-ammeters/0244834/ do the trick if inserted prior to the direction reversing switch?

 

Thanks for you help so far!

 

Alex

[leopardml2341]

Ah, thanks guys! Armed with a couple of searchable terms I came across this basic controller design...

 

 

From this article -> http://www.instructables.com/id/Simple-controllers-for-DC-motors-inc-PWM-inertia/

 

I'm guessing that should do the trick nicely?

 

Presumably an analogue ammeter would be useful. Would one such as this http://uk.rs-online.com/web/p/analogue-panel-ammeters/0244834/ do the trick if inserted prior to the direction reversing switch?

 

Thanks for you help so far!

 

Alex

Used this design for years, without knowing the components from your scheme I'd guess at :

 

VR1 10K linear

R1 1k

TR1 BC108

TR2 2N3055

 

??

 

Instead of using a 1A fuse - use a 12v 12 W car bulb - it limits current to 1A without going pop and will light up when you have an overload.

 

Also 2n3055 (if that's what it is) is way over rated in power handling terms - try the TIP41 family instead.

 

Re ammeter, ones like that are best used as indicators only - I'd put some banana plug sockets on the box then you can use your multimeter, in series for current in parallel for volts - and get a much more accurate measure.

Rgds,

 

Edit - corrects TR2 designation

Edited August 17, 2017 by leopardml2341

[AndyID]

Ah, thanks guys! Armed with a couple of searchable terms I came across this basic controller design...

 

 

From this article -> http://www.instructables.com/id/Simple-controllers-for-DC-motors-inc-PWM-inertia/

 

I'm guessing that should do the trick nicely?

 

Presumably an analogue ammeter would be useful. Would one such as this http://uk.rs-online.com/web/p/analogue-panel-ammeters/0244834/ do the trick if inserted prior to the direction reversing switch?

 

Thanks for you help so far!

 

Alex

 

You could eliminate the first transistor if you use a power darlington instead. Something like a TIP142 or TIP102 will work.

 

However, for your application this regulator will do too good a job. It will maintain the same voltage and supply more current when the locomotive hits a tight spot. You want the voltage to drop so that motor tends to stall if there is a tight spot. That's why you are better with a simple resistor. Best way I know to do that is with a length of nichrome wire between two nails on a plank. You slide a moveable contact (croc-clip) along the wire to change the resistance.  Nichrome is available on Ebay here in the US and it's not expensive. Don't know about the UK.

 

Andy

[Crosland]

You could use a variable voltage regulator such as the LM317, which has built in overload protection.

[brigo]

I use one like this for checking locos, which I bought with a starter set (only bought for the loco, cheaper in the set than buying separate).

 

http://www.ebay.co.uk/itm/Roco-10788-240v-18v-DC-Controller-adaptor-Hornby-R8250-alternative-NEW-UNBOXED-/292046954631?epid=1461367125&hash=item43ff5ae087:g:DLQAAOSwa~BYTR6n

 

It uses the LM317 voltage regulator as Crosland suggests. The output voltage goes up in small steps as the control knob operates a wiper on a set of contacts rather than a potentiometer.

 

Brian

[BG John]

Two ready made LM317s, with potentiometer, for £4!

http://www.ebay.co.uk/itm/2x-LM317-Adjustable-LED-Meter-Voltage-Regulator-Step-down-Power-Supply-Module-/263147319609

 

Various other option are available too if you search for them.

 

EDIT: Just noticed this is an auction, but they're pretty cheap on BINs!

Edited August 18, 2017 by BG John

[AndyID]

Two ready made LM317s, with potentiometer, for £4!

http://www.ebay.co.uk/itm/2x-LM317-Adjustable-LED-Meter-Voltage-Regulator-Step-down-Power-Supply-Module-/263147319609

 

Various other option are available too if you search for them.

 

$8.29 here each, but free shipping! That's from California. Much cheaper if you wait for it to come from China.

 

Here's a link to the supplier of the nichrome wire I was wittering on about. (I'm hoping there may be a similar vendor in the UK)  http://www.jacobs-online.biz/nichrome_wire.htm

 

I bought some 28 AWG and use it to make my own power resistors for experimentation. The thing about power resistors is you never have the one you need and they are not cheap when you have to buy one.

[cliff park]

In the good  (?) old days I have used the element from an old electric fire. Unwind it, it has huge power rating, you might have to scrape it a bit to get a connection. Check out your loft, or car boot sales, but people are wary of selling them because of modern regulations.

[DCB]

$8.29 here each, but free shipping! That's from California. Much cheaper if you wait for it to come from China.

 

Here's a link to the supplier of the nichrome wire I was wittering on about. (I'm hoping there may be a similar vendor in the UK)  http://www.jacobs-online.biz/nichrome_wire.htm

 

I bought some 28 AWG and use it to make my own power resistors for experimentation. The thing about power resistors is you never have the one you need and they are not cheap when you have to buy one.

Can I make a rather blunt assertion that this is the opposite of what you want for testing. It will deliver a set VOLTAGE and vary the current according to the demands of the motor, disguising any tight spots and potentially damaging the gear train.

 

However add a centre off DPDT reversing switch and these will potentially make brilliant controllers for the layout or for running in, very smooth quiet speed stable operation, no angry Bee PWM buzz...

[AndyID]

Can I make a rather blunt assertion that this is the opposite of what you want for testing. It will deliver a set VOLTAGE and vary the current according to the demands of the motor, disguising any tight spots and potentially damaging the gear train.

 

However add a centre off DPDT reversing switch and these will potentially make brilliant controllers for the layout or for running in, very smooth quiet speed stable operation, no angry Bee PWM buzz...

Agreed, and I think that's what I said in post 7 above.

[Rhubarb Loop]

Well,

 

The linked article suggests:

 

VR1 - 10K

TR1 - Any small signal or general purpose NPN such as 2N2222A, BC107, BC109

TR2 - NPN power transistor capable of handling at least 3A and 20V such as TIP31A, TIP31C, TIP41A or 2N3055

F1 -  one amp fuse as some basic overload protection

 

I've tried looking on the Maplin and RS Components for a 10KΩ potentiometer and matching knob, not as easy as I thought. I'm sure we used to use ones like these https://www.maplin.co.uk/p/10k-andohm-miniature-log-single-gang-potentiometer-jm77j all the time when I was at school and there were matching knobs to go with it. I'm looking for something more visually appealing than a bare wire and crocodile clip really, appearance is just as important as function. Ideally a panel mounted knob and direction switch with electrical gubbins hidden out of sight.

 

If the circuit above will actually vary the current (which would hide faults) would I be better old fashioned rheostat controller, perhaps the Hammant and Morgan Minipack?!

 

Cheers,

 

Alex

[dhjgreen]

Well,

 

The linked article suggests:

 

VR1 - 10K

TR1 - Any small signal or general purpose NPN such as 2N2222A, BC107, BC109

TR2 - NPN power transistor capable of handling at least 3A and 20V such as TIP31A, TIP31C, TIP41A or 2N3055

F1 -  one amp fuse as some basic overload protection

 

I've tried looking on the Maplin and RS Components for a 10KΩ potentiometer and matching knob, not as easy as I thought. I'm sure we used to use ones like these https://www.maplin.co.uk/p/10k-andohm-miniature-log-single-gang-potentiometer-jm77j all the time when I was at school and there were matching knobs to go with it. I'm looking for something more visually appealing than a bare wire and crocodile clip really, appearance is just as important as function. Ideally a panel mounted knob and direction switch with electrical gubbins hidden out of sight.

 

If the circuit above will actually vary the current (which would hide faults) would I be better old fashioned rheostat controller, perhaps the Hammant and Morgan Minipack?!

 

Cheers,

 

Alex

I have a Bachmann trainset controller that you can have for the cost of the postage.

[Crosland]

Can I make a rather blunt assertion that this is the opposite of what you want for testing. It will deliver a set VOLTAGE and vary the current according to the demands of the motor, disguising any tight spots and potentially damaging the gear train.

It regulates the voltage but the controller does NOT vary the current. The load (the loco) determines what current is drawn, not the controller.

 

The alternative (resistance) controller has a relatively high resistance and forms a potential divider with the loco. It doesn't regulate either current or voltage in any meaningful way.

[Penrhos1920]

PP3 battery and fly leads

[AndyID]

I have a Bachmann trainset controller that you can have for the cost of the postage.

 

I have a couple of old IR resistance controllers, but you wouldn't want to pay the postage

[kevinlms]

In the good  (?) old days I have used the element from an old electric fire. Unwind it, it has huge power rating, you might have to scrape it a bit to get a connection. Check out your loft, or car boot sales, but people are wary of selling them because of modern regulations.

There is a major significant problem with old electric heaters and that type of thing. Many of these, used a very common material to wind the wire around. That material is ASBESTOS and before dismantling such items for reuse, ought be checked, to see if it contains such material.

 

https://www.airsafe.net.au/news/6-household-items-could-contain-asbestos

 

Since Asbestosis is a slow disease, it might not effect many (most?) members of RMweb, but is it something we MAY inflict of younger family members, to save a few bob?

 

Its a good idea to reuse nichrome wire, but it simply isn't worth the risk, unless known to be clear, IMO.

 

I'll standby for the 'nanny state' comments!

[AndyID]

You can still buy those radiant heater elements in the UK. The support core is ceramic. I believe it always was.

[kevinlms]

You can still buy those radiant heater elements in the UK. The support core is ceramic. I believe it always was.

Older ones could be asbestos. Unless you can be sure, I wouldn't use them. Remember the question was about reusing old ones, not new stock.

 

A club of mine has an old wall mounted hand dryer, which I suspect does contain asbestos.

 

https://www.asbestos.com/occupations/hairdressers/