Fidelity Controller

[B.Meldon]

This post may well generate a bit of interest!!
I half a mind not to say anything about this just yet in case it comes to nought, but.......

In the last few days I have just started working on the circuits from the no longer produced Fidelity Controller that was previously made in New Zealand. All the information, including the schematics, the PCB board track design, component lists and component locations on the PCB was provided by the original manufacture. In fact everything needed to make this controller myself. This is a 100hz variable voltage feedback controller that avoids all the problems of PWM feedback by using a constant waveform that is suited to both the older 'iron core' motors and with the newer low current so called 'coreless' motors.
In this respect it may well turn out to be bit of a 'holy grail' in terms of DC controllers as in practice it does indeed work very well with both types of motors with excellent low speed control, in fact probably as good as the best slow speed control I have ever seen in a DC controller. In this respect it is not dissimilar to the slow speed control obtained with DCC.
It is based around three ic's; an LM324, LM3900 and NE5537N with a BD679 output trans.

My initial intension is to build one controller without the brake and throttle simulation using the details provided for testing purposes. If all is successful and it performs as good as the original with a wide range of motors, I may then simplify the PCB, removing the sections for the simulator that are not required and then build five or six for my own use on my layouts.

Depending on the results of the above and more discussions with the original manufacture there may be a next step. But that will be some time off.

[Hugh Norwood]

Did you pay for the details, Brian? And if not, would you be prepared to send me them, please? I "collect" controller circuits.

[Graeme Dunbar]

I'm interested too Brian, if it is not breaking any non-disclosure agreement.

What you write has piqued my interest, with effectively nine operational amplifier elements in the packages you list it sounds like quite a sophisticated design. I'm also interested in knowing the vintage of the circuit. I'd hazard a guess from the combination of devices no earlier than the mid 1980s.

(It seems certain component combinations are in vogue at different times. It was one of the things we talked about at the meeting - the use of unijunction transistors in a number of designs still in use dates them.)

[B.Meldon]

Sorry but the info. is very much for my personal use only at this stage.
It is all hand drawn info. and the scans are not great. Some of the component descriptions were illegible and others not quite complete. As a result it took some time for me to work out what some of the components were!

The first task is to clean up the PCB drawing as it is quite poor quality and not suitable for etching as it is.
It also needs re-sizing before it can be used.
This will take a few days work.
I have not done any etching for many years so I will have to get all the materials again.
I have also not used my current laser printer for etching, so it may not work as well as the old one from the 80's.

By good fortune I have a close relative who is a director of an electronics manufacturing company here in Essex, and this may come in handy at some point in the future if all goes to plan.

[Graeme Dunbar]

That sounds like an interesting project Brian. That's keen, etching your own boards! These days sending Gerber files to one of the PCB manufacturers in China seems to be the most popular approach.

[B.Meldon]

That sounds like an interesting project Brian. That's keen, etching your own boards! These days sending Gerber files to one of the PCB manufacturers in China seems to be the most popular approach.

I have done simple PCB's before, but not for many years. Thinking about it it was probably almost 30 years ago now!
I will see how I get on, it may be a disaster!!

[Alan Feldon]

Well done Brian I know Richard Glover was in correspondence with the original maker .
I certainly would not do without mine as it seems to run anything and totally controllable .
Alan

[B.Meldon]

Well done Brian I know Richard Glover was in correspondence with the original maker .
I certainly would not do without mine as it seems to run anything and totally controllable .
Alan

Yes the info came via Richard.

[B.Meldon]

That sounds like an interesting project Brian. That's keen, etching your own boards! These days sending Gerber files to one of the PCB manufacturers in China seems to be the most popular approach.

Is there a free JPG to Gerber converter?

[Graeme Dunbar]

That sounds like an interesting project Brian. That's keen, etching your own boards! These days sending Gerber files to one of the PCB manufacturers in China seems to be the most popular approach.

Is there a free JPG to Gerber converter?

I doubt it unfortunately. Gerber files contain all sorts of parametric information about the board beyond the routing of track as far as I'm aware, at least as far as a commercial PCB manufacturer require. Its origins are in graphics plotter type situations for line drawing rather than bitmapped images. Going the other way, from Gerber to an image format or PDF on the other hand poses no problems!

[B.Meldon]

That sounds like an interesting project Brian. That's keen, etching your own boards! These days sending Gerber files to one of the PCB manufacturers in China seems to be the most popular approach.

Is there a free JPG to Gerber converter?

I doubt it unfortunately. Gerber files contain all sorts of parametric information about the board beyond the routing of track as far as I'm aware, at least as far as a commercial PCB manufacturer require. Its origins are in graphics plotter type situations for line drawing rather than bitmapped images. Going the other way, from Gerber to an image format or PDF on the other hand poses no problems!

That sounds a bit complicated for me, and I would guess that the software involved is quite expensive as well.
It would be quite an effort to convert the hand drawn documentation I have into this form.

However, if the end result turns out to be as good as i think it could be, it may well be worth the time and effort.

I am going to have a chat with my relative who is a director of an electronics manufacturing company this weekend to get their thoughts on this.

[Graeme Dunbar]

That sounds like an interesting project Brian. That's keen, etching your own boards! These days sending Gerber files to one of the PCB manufacturers in China seems to be the most popular approach.

Is there a free JPG to Gerber converter?

I doubt it unfortunately. Gerber files contain all sorts of parametric information about the board beyond the routing of track as far as I'm aware, at least as far as a commercial PCB manufacturer require. Its origins are in graphics plotter type situations for line drawing rather than bitmapped images. Going the other way, from Gerber to an image format or PDF on the other hand poses no problems!

That sounds a bit complicated for me, and I would guess that the software involved is quite expensive as well.
It would be quite an effort to convert the hand drawn documentation I have into this form.

However, if the end result turns out to be as good as i think it could be, it may well be worth the time and effort.

I am going to have a chat with my relative who is a director of an electronics manufacturing company this weekend to get their thoughts on this.

I think it depends quite a lot on what one is familiar with. Learning to use new and quite complex software for one or a small number of jobs is probably not a good use of time. On the other hand if one already has those skills, designing a circuit board in the software is probably a lot quicker than doing it by hand. As for the software, yes there are some very expensive commercial offerings but there are also ones available for free. Some of these may tie the user into one supplier or have other limitations. One that seems popular currently is KiCAD. I'm currently learning it because the one I'm most familiar with (Eagle CAD) used to be free but has gone through at least a couple of stages of commercialization and unless the current fully paid up version has significant improvements, is looking decidedly clunky in a number of aspects.

If you have a relative in the electronics business then is asking them if it would be possible to turn the schematic into a PCB track layout a way forward? If you have plans for the boards to be etched professionally by them, based on your prototype, they are quite likely to do so anyway.

One advantage of using CAD software is that it can check for consistency between the schematic and board layout and warn of missing connections or shorts and even simulate the circuit and do thermal modelling (depending on software sophistication and circuit complexity), generate an inventory, allow relatively easy swapping of equivalent devices that may only be available in different footprints (in case of component availability problems etc.)