Pentrollers

Discussions of the prototypes and how to model them. Show us how you do it.
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John McAleely
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Pentrollers

Postby John McAleely » Mon Jun 02, 2014 11:18 am

Would now be a good moment for this newbie to ask just what is so special about a pentroller? They seem to be spoken of reverently, but aren't they just some transistors and a variable resistor?

[Edit: split from a thread discussing the sale of a pentroller on eBay]
Last edited by John McAleely on Sun Aug 10, 2014 5:57 pm, edited 1 time in total.
Reason: Split from for-sale thread

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Tim V
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Re: Pentroller for sale.

Postby Tim V » Mon Jun 02, 2014 11:38 am

They were good, in there day. Quite good on Portescaps. There was a switch for different motor types.

Back in the 80s, a Pentroller, with Portescaps were the bees knees in controllability.

However, they are no longer supported by Stewart Hine. Also, the pots wore out (I replaced mine quite a few times), reputed to be the loading through the pot. It was that problem that encouraged me to get rid of my Pentrollers (to good homes).

The thing is that controllers have moved on a long way from the Pentroller, which dates back to the 80s I think. The Pictroller is reputed not to be as good, hence Pentrollers are sought after.

I'd rather spend my money on DCC with decent chips which mean you can fine tune the control specific to each loco, rather than the switch on the controller. Portescaps too are now old hat, they were used to overcome a problem that no longer exists. There are better motor/gearbox combinations available, that mean we have moved on a long way from 80s technology.
Tim V

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John McAleely
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Re: Pentroller for sale.

Postby John McAleely » Mon Jun 02, 2014 1:13 pm

Tim V wrote:They were good, in there day. Quite good on Portescaps. There was a switch for different motor types.


OK, so that must mean they do 'something specific' electrically. I don't understand why that can't be replicated by a modern design. Even if it was just a design you had to build, I sense that it would remain popular.

I'm with you on the details of why I wouldn't choose them now.

JFS
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Re: Pentroller for sale.

Postby JFS » Mon Jun 02, 2014 2:15 pm

John McAleely wrote:
Tim V wrote:They were good, in there day. Quite good on Portescaps. There was a switch for different motor types.


OK, so that must mean they do 'something specific' electrically. I don't understand why that can't be replicated by a modern design. Even if it was just a design you had to build, I sense that it would remain popular.

I'm with you on the details of why I wouldn't choose them now.


Yeh, they are not worth the hassle - completely unreliable, really poor control, motors jumping and stuttering all over the shop. Rubbish really.

And you can't repair them as a number of the components are no longer manufactured...

I definitely would not bid if I were you...

PS I see Jol has not answered my post above...

Cheers,

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Will L
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Re: Pentroller for sale.

Postby Will L » Mon Jun 02, 2014 3:08 pm

John McAleely wrote:OK, so that must mean they do 'something specific' electrically. I don't understand why that can't be replicated by a modern design.


Pentrollers are feedback controllers that adjust the power fed to the motor based on the back EMF generated by the motor. they are capable of controlling how fast the motor turns regardless of train weight and gradient, within the performance limits of the motor. This is exactly the same trick as the DCC chips use. The idea first marketed in Compspeed controllers (DC). They all work by pulsing the motor and measuring the voltage generated by the motor between pulses. The the original Compspeed pulsed too slowly and coreless motors didn't take kindly to them, pushing up the plus rate fixes the problem. The Pentroller motor type switch (choice big coreless, small coreless, or iron core) is as much to do with the max current allowed by the overload protection circuit than anything else.

Since the advent of descent quality of iron cored can motors, problems with feedback controllers and expensive and delicate coreless motors are as good a reason not to bother with coreless motors than anything else.

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Jol Wilkinson
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Re: Pentroller for sale.

Postby Jol Wilkinson » Tue Jun 03, 2014 6:53 am

JFS wrote:
Jol Wilkinson wrote:I am following this on ebay. It has almost reached the price of a new Pictroller and although I really like Pentrollers (I already have two like this on London Road plus a HH) I am inclined to think it may not be a good buy if it goes up much more. With six days still to go that is more than likely.

Jol



Do I understand you to say Jol, that if I were to give you two Pictrollers, plus, say 30 quid, you would send me one panel mount and one HH Pentrollers? (If you say "yes", they will be in the post this afternoon!!)

Best wishes,

Howard


Howard,

no, but thanks for the offer. I don't want to part with what I have and which took me some time to collect. I've also got two of the small panel mounts mounted into boxes to make them into HHs for larger hands as well as another original HH that doesn't work properly. London Road needs four controllers so that gives me one spare.

It's the apparent fragility of the Pentroller and the lack of a repair facility for them since Stewart Hine retired several years ago, that makes me reluctant to buy another at a high price since the Pictroller came onto the market.

Jol

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Jol Wilkinson
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Re: Pentroller for sale.

Postby Jol Wilkinson » Tue Jun 03, 2014 7:05 am

In response to those that have commented on the "performance" of the Pentroller, they were designed with a feedback circuit that would work with coreless motors without damage to the lightweight brush gear. I believe this was achieved by using a very high frequency in the feedback circuit. The late Mike Grey (a modeller and a professor of electrical engineering who designed the LRM RSU) used an oscilloscope to work out what was going on, but couldn't identify the circuit design as the markings had been erased from the chips.

At the time they were - and probably still are - the best design of DC controller made. I also have a Modelex unit, which as a straightforward controller is also very good.

Jol

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Captain Kernow
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Re: Pentroller for sale.

Postby Captain Kernow » Tue Jun 03, 2014 8:44 am

JFS wrote:Yeh, they are not worth the hassle - completely unreliable, really poor control, motors jumping and stuttering all over the shop. Rubbish really.

And you can't repair them as a number of the components are no longer manufactured...

I definitely would not bid if I were you...

Well thanks for that, at least we've got to £70 on the bid, even if no one else bids...

I'd just politely remind everyone that we are trying to raise funds for one of our own Area Groups here, for what is a worthy P4 layout project with an interesting history...



(Unless the comment was tongue-in-cheek, of course, in which case I'll shunt the sarcastic wagon back to the cripple siding...)
Tim M
Member of the Devon Riviera Area Group.

JFS
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Re: Pentroller for sale.

Postby JFS » Tue Jun 03, 2014 9:52 am

Jol Wilkinson wrote:
Howard,

no, but thanks for the offer.

Jol


:D :D I don't blame you but it was worth a punt!!!

In truth the Pictroller is much the best of the ones I have tried - though the feedback is nowhere near as sensitive as the Pentroller's.

But there are three pretty major (to me) faults - firstly on small Portescaps, the "sensing pulse" causes a very distinct "kick" utterly destroying all realism and probably not too good for the motor.
Secondly, if a loco stops on a bit of crud the controller starts to ramp up the voltage - causing the loco to shoot off after a second or two before it stablises.
Thirdly, it does not respond to sudden movements of the knob. Not that such things ever happen in an operating session - but when "testing", and your prize loco is heading towards the stops at a rate of knots and you want to stop it quickly...
(no doubt this is down to the polling rate of the position sensor on the knob). When people say "well, it does not do any of that for me" I ask" do you use Portescaps???" ... well I do!
Of course, it could be that there are later versions of firmware available to correct such issues, but I am not aware of any means of updating the firmware.

At the other end of the scale I also have some Bachmann EMUs - with the Pentroller, I know the track / wheels need cleaning when the lights are flickering madly as the unit crawls along at a rock steady walking pace...

And, Tim's comments notwithstanding, I would back a 30year old Portescap and Pentroller against anything for controllability. (the Portescap needs to be that old as the delrin gears started to evolve into shapeless and very noisy blobs due to mould wear soon after that!)

Best wishes,

martin goodall
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Re: Pentroller for sale.

Postby martin goodall » Tue Jun 03, 2014 11:35 am

At the slight risk of pursuing a discussion which may be going off-thread (and certainly doesn't belong within this subject heading on the forum), I was interested to read JFS's remarks about the PICtroller, as I have identified the same points myself on my recently purchased panel-mounted PICtroller. They do not seem to occur (or are less noticeable) on the hand-held PICtroller.

I am sure that Malcolm Smith would be willing to discuss these point with users, and he may well be prepared to consider some modification to the circuitry to address this issue; I haven't had time yet to contact him about this.

It is worth remembering that we are not dealing with faceless big business here, but with a fellow hobbyist, who is very much a part ofthe finescale community and who no doubt is as interested as the rest of us in 'improving the breed'.

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Re6/6
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Re: Pentroller for sale.

Postby Re6/6 » Tue Jun 03, 2014 12:15 pm

JFS wrote:Yeh, they are not worth the hassle - completely unreliable, really poor control, motors jumping and stuttering all over the shop. Rubbish really.

And you can't repair them as a number of the components are no longer manufactured...

I definitely would not bid if I were you...


As has been said, we (DRAG) are trying to raise funds for the restoration of what was a very fine layout, professionally built by a very well known and respected model builder.

Some will know that it was built as a permanent set up. We are rebuilding a completely new ‘undercarriage’ for it, as the original was built from heavy chipboard and Dexion angle. We are also building a new extended ‘country’ section. In due course it will be exhibited.

All this work won’t come cheap and as we are only a relatively small group, funding for completion is quite tight.

The administrators on here were kind enough to allow me to alert members to the sale of it on eBay.

If I’d have thought that this sort of negativity on a publicly accessible forum would result, I wouldn’t have bothered. We just hope that it does well in the end.

These sort of opinions would certainly be acceptable on a general thread about Pentrollers, but not on one where a member is trying to sell an item on behalf of a society area group.
Last edited by Re6/6 on Tue Jun 03, 2014 12:28 pm, edited 1 time in total.
John

JFS
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Re: Pentroller for sale.

Postby JFS » Tue Jun 03, 2014 12:28 pm

martin goodall wrote:I am sure that Malcolm Smith would be willing to discuss these point with users...


Very fair point Martin and I hope I did not give an impression that I was a dissatisfied customer - as I said, I still feel that the Pictroller is the "best of the rest" so the "faults" (which I understand are rather features of the digital technology) would not stop me buying another.

That said, the website says that they are "in the process of closing down" so I am not sure if even Pictrollers will remain an option for long?

Best wishes,

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John McAleely
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Re: Pentroller for sale.

Postby John McAleely » Tue Jun 03, 2014 12:35 pm

Re6/6 wrote:
JFS wrote:Yeh, they are not worth the hassle - completely unreliable, really poor control, motors jumping and stuttering all over the shop. Rubbish really.


If I’d have thought that this sort of negativity on a publicly accessible forum would result, I wouldn’t have bothered. We just hope that it does well in the end.


Given the earlier comment by the same author, wanting to obtain the controllers by other means too, I read that comment as tongue in cheek.

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grovenor-2685
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Re: Pentroller for sale.

Postby grovenor-2685 » Tue Jun 03, 2014 12:41 pm

If I’d have thought that this sort of negativity on a publicly accessible forum would result, I wouldn’t have bothered.

Just for clarity here, Sales and Wants is NOT publically accessible, it is a member's only section. Even so this is not the place for discussion of the merits and demerits of different controllers.
Regards
Keith

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John McAleely
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Re: Pentroller for sale.

Postby John McAleely » Tue Jun 03, 2014 1:08 pm

grovenor-2685 wrote:
If I’d have thought that this sort of negativity on a publicly accessible forum would result, I wouldn’t have bothered.

Even so this is not the place for discussion of the merits and demerits of different controllers.


Agreed. I'll move most of this thread elsewhere. Given how ebay works, I'll probably wait for this sale to finish, and then also delete the link to it at the same time. We'll be left with a discussion of the pentroller, etc.

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Re6/6
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Re: Pentroller for sale.

Postby Re6/6 » Tue Jun 03, 2014 3:31 pm

Thank you Keith and John.

Removal of the OP would be appreciated..
John

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Paul Townsend
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Re: Pentroller for sale.

Postby Paul Townsend » Wed Jun 04, 2014 6:25 am

JFS wrote:That said, the website says that they are "in the process of closing down" so I am not sure if even Pictrollers will remain an option for long?
,


I cant see any mention of that on their site.

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Ian Everett
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Re: Pentroller for sale.

Postby Ian Everett » Wed Jun 04, 2014 7:00 am

Paul Townsend wrote:
JFS wrote:That said, the website says that they are "in the process of closing down" so I am not sure if even Pictrollers will remain an option for long?
,


I cant see any mention of that on their site.


See Finney and Smith's home page - http://finneyandsmith.co.uk/finneyandsmith/index.htm

Another one bites the dust - bad news for 3mm scale modellers.

Ian

nigelcliffe
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Re: Pentroller for sale.

Postby nigelcliffe » Wed Jun 04, 2014 7:37 am

Ian Everett wrote:
Paul Townsend wrote:
{ on whether Pictrollers are about to cease to be available }

I cant see any mention of that on their site.


See Finney and Smith's home page - http://finneyandsmith.co.uk/finneyandsmith/index.htm

Another one bites the dust - bad news for 3mm scale modellers.

Ian


Finney and Smith are a retailer who sell the Pictroller (the "Smith" is Nick Smith).
The manufacturer is Malcolm Smith, of Malcolm's Miniatures.

http://www.malcolmsminiatures.co.uk/
( link in bottom of left column to model railway controls )

So, it appears that a retailer is closing, not a manufacturer.



- Nigel

martin goodall
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Re: Pentroller for sale.

Postby martin goodall » Wed Jun 04, 2014 4:38 pm

nigelcliffe wrote:
Finney and Smith are a retailer who sell the Pictroller (the "Smith" is Nick Smith).
The manufacturer is Malcolm Smith, of Malcolm's Miniatures.

http://www.malcolmsminiatures.co.uk/
( link in bottom of left column to model railway controls )

So, it appears that a retailer is closing, not a manufacturer.



- Nigel


PICtrollers are sold direct by Malcolm Smith. I ordered mine from him via his 'Malcolm's Miniatures' website.

Incidentally, back OT, if the second-hand Pentroller advertised here is still avialable, it would certainly be worth considering as an alternative.

JFS
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Re: Pentroller for sale.

Postby JFS » Wed Jun 04, 2014 7:44 pm

martin goodall wrote:
PICtrollers are sold direct by Malcolm Smith.


Many thanks for this clarification Martin - I for one was not aware of this (I got mine via Finney and Smith at Scaleforum). A Google search for "Pictroller" only throws up the Finney and Smith site. A search for images only throws up Malcolm's site in relation to a DIN socket.

This might be worth mentioning to Malcolm if anyone here is in contact with him - if Google's bots can't sniff it out, what chance us humans!!

Best wishes,

nigelcliffe
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Re: Pentroller for sale.

Postby nigelcliffe » Wed Jun 04, 2014 10:03 pm

JFS wrote:This might be worth mentioning to Malcolm if anyone here is in contact with him - if Google's bots can't sniff it out, what chance us humans!!


Google is searching/indexing Malcolm's pages, but not rating them very highly so they don't appear when searching. Best solution is for lots of people to add links from their sites (including Blogs, particularly Google Blogger blogs) to him; that's the cheap way to boost a rating.

(The best way to get to the top of a Google search is to start your website before 1996.... Then Google found you at the beginning, and its not hard to stay well up a search ranking. ).


- Nigel

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Russ Elliott
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Re: Pentroller for sale.

Postby Russ Elliott » Thu Jun 05, 2014 12:44 pm

JFS wrote:if Google's bots can't sniff it out, what chance us humans!!

http://clag.org.uk/russ/supplier.html


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