21 replies to this topic

[NorCalJim]

Greetings!

 

I plan to replace the bridge rectifiers on a 1/24 scale Cidex Omni controller to tame the sensitivity performance so that it is more suitable for 1/32 scale use and I am looking for a bridge rectifier parts recommendation.

 

Lately, I have been lining up a number of controller-related projects since I am mostly sheltering in place due to the pandemic.  I am highly nostalgic and have been thinking about diode-based voltage divider type controllers and their versatility.  I had two diode-based Professor Motor (PMTR2059) "Gold" model controllers from the "Silver Series" that I initially used with HO magnet cars through Champion Group 12 cars.  Recently, I had the opportunity to purchase three Cidex Omni controllers (Parma Turbo upgrade type for 1/24).  Much of my attraction to the Cidex Omni is that they are also voltage divider type controllers.  The first one that I purchased was in excellent condition and while able to control one of my NSR cars on my routed 53' lap length 1/32 scale track, the sensitivity was really high.  My two addition purchases have not yet arrived and I expect that one or both will need repairs and bridge rectifier replacements (my reason for seeking advice on tuning the controller for 1/32 cars).

 

Why would I go through the trouble when there are much better controller options available?  I have a plethora of controllers to choose from but I want to explore a real classic.  Like the Jay Leno's Garage series on YouTube and his continual enjoyment of automotive wonders, I am exploring some controllers that have been super-ceded by current models.  

 

- Jim

[bbr]

google search "diode low voltage drops"

[Jim Difalco]

Omni HO controllers had more diodes than 1/24 models. You would actually want high voltage drop diodes, or add more diodes.

[NorCalJim]

Omni HO controllers had more diodes than 1/24 models. You would actually want high voltage drop diodes, or add more diodes.

 

Thank you, Jim!  The Cidex Omni HO controllers use 8 bridge rectifiers with no heat sink fins.  My Cidex Omni controllers are the 1/24 type with the heat sink fins interspersed with 6 bridge rectifiers (the last one dedicated to the 4 way selectable braking (from full brakes to no brakes) and the other 5 available for an adjustable power curve with 3 sensitivity selections.  Larry Kelley cited two bridge rectifier parts in one of his posts (KBU8... and GBU8...) in relation to the 1/24 controller.  Now I'm wondering whether it would be feasible to try and turn the 1/24 Omni into a 1/32 controller.

This is strictly for fun and learning.  I have plenty of 1/32 scale controllers including your DD302 with traction control (very impressive).

 

- Jim Person (long time Difalco Designs customer)

[Jim Difalco]

Jim, I know you run my controllers so thanks for being a customer.

[Jim Difalco]

The Cidex was a hot ticket for a few years way back when. A fact that no one knows is that the owner, I forget his name, asked me to build the controllers for him. Install his unit on Parma turbo frames then ship it back to him. I was building my external controllers back then and had no intention of helping him and his business that I was competing against. He even gave me a module to install in a controller for testing purposes. When I turned down his offer to build his controllers he asked for the module to be returned. I told him no and that annoyed him the entire time he was in the slot business. I still have the totally new Omni module in my collection today, never used! No Jim, you cannot buy it!

[Bill Seitz]

I remember when the Cidex controllers became available. I understood they were supposed to self-adjust to the motors being used and needed no sensitivity adjustment. As I studied rectifier diode spec sheets, it was obvious this was not the case. The diode forward voltage drop varies directly with current. As the current increases, the voltage drop increases. This is opposite of what needs to happen in a slot car controller. You may find a rectifier that has higher voltage drop than the ones being used, but usually the only way to increase sensitivity (lower the controller's starting voltage) is to add diodes. Most common bridge rectifiers have a rated forward voltage drop of 1 to 1.1 volts at rated current which drops toward .6 volts as the current decreases from rated. Schottky diodes have approximately half as much forward voltage drop. I had intended to build a diode controller, but adjusting sensitivity becomes an exercise in switching multiple diodes in and out of the circuit and limits the size of steps from start voltage to full power. I decided to go with the commonly used transistor controller.

 

I've never owned a Cidex, so don't know what current rating rectifiers were used. As I recall, there were different sized ones with the two on the larger heatsink likely being 25 or 35 amp. For a 1/32 scale controller, lower current rated rectifiers could be substituted for all, and that would increase the effective voltage drop across each one, but I expect this will still not be an adequate conversion. Additional diodes will need to be added to the circuit. The other issue will be how many steps are available. 1/24 controllers of that era tended to have 6 to 10 steps which I anticipate will be coarse for a 1/32 car usually running on a smaller track.

 

Bill

[NorCalJim]

The Cidex was a hot ticket for a few years way back when. A fact that no one knows is that the owner, I forget his name, asked me to build the controllers for him. Install his unit on Parma turbo frames then ship it back to him. I was building my external controllers back then and had no intention of helping him and his business that I was competing against. He even gave me a module to install in a controller for testing purposes. When I turned down his offer to build his controllers he asked for the module to be returned. I told him no and that annoyed him the entire time he was in the slot business. I still have the totally new Omni module in my collection today, never used! No Jim, you cannot buy it!

 

Interesting history, Jim.  I missed the Cidex heyday since the last commercial raceway where I lived at the time closed in 1974 and I didn't rediscover the existence of slot cars until the late 90s.  So, it's fun to get a close look at the Cidex during this pandemic even if I'm not a fan of the large heat sink fins (makes sense for 1/24 but not needed for 1/32).  

 

- Jim

[NorCalJim]

I remember when the Cidex controllers became available. I understood they were supposed to self-adjust to the motors being used and needed no sensitivity adjustment. As I studied rectifier diode spec sheets, it was obvious this was not the case. The diode forward voltage drop varies directly with current. As the current increases, the voltage drop increases. This is opposite of what needs to happen in a slot car controller. You may find a rectifier that has higher voltage drop than the ones being used, but usually the only way to increase sensitivity (lower the controller's starting voltage) is to add diodes. Most common bridge rectifiers have a rated forward voltage drop of 1 to 1.1 volts at rated current which drops toward .6 volts as the current decreases from rated. Schottky diodes have approximately half as much forward voltage drop. I had intended to build a diode controller, but adjusting sensitivity becomes an exercise in switching multiple diodes in and out of the circuit and limits the size of steps from start voltage to full power. I decided to go with the commonly used transistor controller.

 

I've never owned a Cidex, so don't know what current rating rectifiers were used. As I recall, there were different sized ones with the two on the larger heatsink likely being 25 or 35 amp. For a 1/32 scale controller, lower current rated rectifiers could be substituted for all, and that would increase the effective voltage drop across each one, but I expect this will still not be an adequate conversion. Additional diodes will need to be added to the circuit. The other issue will be how many steps are available. 1/24 controllers of that era tended to have 6 to 10 steps which I anticipate will be coarse for a 1/32 car usually running on a smaller track.

 

Bill

Thanks, Bill!  I appreciate your thoughts on the subject.  I haven't gone over my Cidex with a multi-meter but it looks to be in excellent condition.  It does work with the NSR car that I used for an initial driving impression.  The sensitivity just needs to be dialed down and you've given me plenty to think about.

 

- Jim

[Rob Voska]

Larry Kelly knows a LOT about Omni's.  Not sure about the HO or 1/32.

[Phloidboy1]

CIDEX Omni Controller Wiring Diagram/Schematic....please, specifically, where does the Red wire go ?

Your assistance in helping with this inquiry is greatly appreciated in advance. Thx, Floyd

[groupracer]

If this is still a valid thread, see this:  https://lambdageeks....e-voltage-drop/

[Bill Seitz]

The problem with the linked article is that it's the simple view of forward voltage drop; "about .7 volts". Actually the voltage varies with current from well below .7 volts at small currents to 1 volt or more at rated current for the diode. This can make it difficult to get just the right sensitivity for a variety of different performance motors. The diode controller works by having a series string of diodes for their voltage drops with taps at appropriate steps in the string for the controller throttle response. It's a simple idea, but I've never seen a diode controller with any sort of sensitivity adjustment which requires adding or subtracting diodes in the string using switches.

[Phloidboy1]

back to #11, original inquiry of termination location of red wire, thx

[Paul5097]

Here is a picture of mine. Hope it helps. After taking the picture, I noticed how crappy the soldering looks. I may clean that up. But it works.

 

[Phloidboy1]

other end of red wire, down in handle, thx

[Phloidboy1]

 does anybody know where other end of red wire, going down into the handle terminates, thx, floyd

[Paul5097]

On my controller, it goes  through a self-resetting fuse on its way to the red alligator clip (brake wire)

 

[Phloidboy1]

OK, Thanks, it's getting clear now, but what's the yellow thing, a diode? #ECE BU160 190?

[Paul5097]

That is a self-resetting fuse. It has been used on controllers for quite a while. You can get them from Difalco.

 

This one would work.

https://www.digikey....6R250GU/1985468

[Phloidboy1]

thank you

[Ramcatlarry]

My name was dropped, but I just now read this thread.  The difference in the standard Omni and the "Euro" models is the use of higher voltage drop glass passivated rectifiers (GBU8) instead if the standard silicone rectifier (KBU8).  The earlier ProfMotor controllers that used diodes were designed to work with the 1/32 cars like Carrera and NSR.  These have been phased out in favor of transistorized controllers as have Difalco currently offer.  More diode steps works better than fewer, but still has notchy steps instead of super smooth new tech.