55 replies to this topic

[Rob Voska]

Another idea.  Have more then 1 chip & an A,B,C selector switch or at lease a second socket to store the extra chip or two.  Even on the lower box would be nice.

[dtosetto]

Another idea.  Have more then 1 chip & an A,B,C selector switch or at lease a second socket to store the extra chip or two.  Even on the lower box would be nice.

Thank you for the idea.

[Greg Erskine]

Is the DH45 transistor in the schematic actually a D45H?

[dtosetto]

Please datasheet attached.

Attached Files

•  D45H PNP Power low CE drop.pdf   68.32KB   114 downloads

[Greg Erskine]

That is what I have been using in spice simulations.

 

It seems a very high powered transistor in a low power situation?

[dtosetto]

That is what I have been using in spice simulations.
 
It seems a very high powered transistor in a low power situation?

Please contact JCS100 from slot forum, the is the person that create the diagram, he will be the best one to answer this question.

[Revtor]

That is what I have been using in spice simulations.

 

It seems a very high powered transistor in a low power situation?

Not much drawback in using a higher rated transistor.  If it fits, if it can handle the current, if it can take the heat, if the specs line up with what you need, then go for it.  Its not the steady current draw that kills these, its the spikes from "GO", track calls, back EMF, etc etc that kills them.  Having a more robust transistor that can handle these conditions seems like a good idea. ***

 

Dtosetto, perhaps having areas on the pcb's with open pads/vias for adding parts cleanly for experimenters?  Also, open pads on the traces so things can be modified by cutting traces and adding wires would really open the "open source" concept a bit I think.

 

~Steve

 

*** I'm NOT an EE!!

[dtosetto]

Not much drawback in using a higher rated transistor.  If it fits, if it can handle the current, if it can take the heat, if the specs line up with what you need, then go for it.  Its not the steady current draw that kills these, its the spikes from "GO", track calls, back EMF, etc etc that kills them.  Having a more robust transistor that can handle these conditions seems like a good idea. ***
 
Dtosetto, perhaps having areas on the pcb's with open pads/vias for adding parts cleanly for experimenters?  Also, open pads on the traces so things can be modified by cutting traces and adding wires would really open the "open source" concept a bit I think.
 
~Steve

Please send me you email address and I will share the easyeda source file with you before I publish on the web.
 
*** I'm NOT an EE!!

[Greg Erskine]

Not much drawback in using a higher rated transistor.  If it fits, if it can handle the current, if it can take the heat, if the specs line up with what you need, then go for it.  Its not the steady current draw that kills these, its the spikes from "GO", track calls, back EMF, etc etc that kills them.  Having a more robust transistor that can handle these conditions seems like a good idea. ***

 

Dtosetto, perhaps having areas on the pcb's with open pads/vias for adding parts cleanly for experimenters?  Also, open pads on the traces so things can be modified by cutting traces and adding wires would really open the "open source" concept a bit I think.

 

~Steve

 

*** I'm NOT an EE!!

 

*** I'm NOT a EE either. WARNING: I know *just* enough to be dangerous.

 

I just think its ironic that a darlington circuit is used to enable the use of a low current control circuit (20mA??) then a power transistor (10A peak 20A) is used. Usually over specing a component comes at a sacrifice, something like having a high current capacity might mean it has a low hfe or high Cob.

 

I think transient voltages can be high but little current ???

 

The back EMF of the relay coils is handled by suppression diodes, although on the commercial controllers I have looked at they don't fit them at all !! Maybe because fitting suppression diodes slows the operation of the relay.

 

I think the back EMF of the motor is dealt with in the brake circuit which is effectively a shortcut.

[Revtor]

Greg I haven't even looked at the schematic, and so yeah a darlington to drive the control circuit to then drive the final output stage does seem odd.  I'm sure it was arrived at by trial and error though. (maybe?)

And thats whats great about the OS controller idea, letting anyone with the interest try things out.  Im under no impression that what I could come up with is in anyway going to make waves or challenge the current transistor controllers out there, but I just love tinkering with electronics.

[Guy Spaulding]

Correct me if I'm wrong but antibrake simply turns the brake band off (isolates it) and routes the first band power through the brake pad. (not contact)

Absolutely true.  (1st or 2nd band), then a pot to adjust

[Greg Erskine]

I am not sure how anti-brake's are implemented, but generally the first band voltage will vary depending on the setting of the "sensitivity" and the "resistor network" used. Some people adjust the first band to be sufficient for their slot car to just run. This may be too fast for an anti-brake system. A fully adjustable and independent system seems desirable.

 

I hope Daniel is concentrating on getting the "basic" prototype done. These nice options will be great future project.

[Greg Erskine]

Greg I haven't even looked at the schematic, and so yeah a darlington to drive the control circuit to then drive the final output stage does seem odd.  I'm sure it was arrived at by trial and error though. (maybe?)

And thats whats great about the OS controller idea, letting anyone with the interest try things out.  Im under no impression that what I could come up with is in anyway going to make waves or challenge the current transistor controllers out there, but I just love tinkering with electronics.

 

+1

 

I have full confidence in the designer JCS100. He knows what he is doing, plus more importantly, he has had decades of practical experience with slot car controllers. The darlington circuit is commonly used in the UK. I have a feeling the D44H/D45H might be the "goto" transistor having a wide spec. Again it feels to me it is often mentioned in general UK forums (only a feeling no proof).

[Rob Voska]

Anti-brake with a timer so you don't drive into crashes or marshals hands.

 

Darlington pair.  The disadvantage is powering 2 transistors.  Aprox 0.6v drop each.  So when teh clicker box is used you have full track power but as soon as it disconnects you are down ~1.2v and that is a pretty big step.  That is why they are making fet controllers.

 

I might add it's also very much a what class / motor you run issue.

[Greg Erskine]

This particular darlington circuit has the last band of the wiper connected directly to the base of the output transistors bypassing the driver transistor, so there is effectively 2 fixed 0.6V steps. I haven't seen that done before.

 

In my simulation (could be wrong), Vbe seems to increase with current, the opposite of what you want.

[Greg Erskine]

Are there any legitimate schematics of anti-break systems?

 

I find it hard to understand word descriptions of circuits.

[iv_man]

Anti-brake with a timer so you don't drive into crashes or marshals hands.

 

Darlington pair.  The disadvantage is powering 2 transistors.  Aprox 0.6v drop each.  So when teh clicker box is used you have full track power but as soon as it disconnects you are down ~1.2v and that is a pretty big step.  That is why they are making fet controllers.

 

I might add it's also very much a what class / motor you run issue.

I've built a variety of different controllers over the years; transistor, FET switching, contact-less wipers, combos of both with software and with more traditional control (say typical of Difalco, Czech Pro etc.)

 

But I've never understood why it's believed that Darlington pairs drop the voltage twice.  I'm not an expert and I must admit that I have never tried to measure the difference.  But when you see the diagram here I can see the Base to Emitter relationship has a double voltage drop.  But the motor load is carried Collector to Emitter where there is only one voltage drop.

 

Can anyone explain this (simply!)??  Err,..... asking for a friend......

[smichslot]

Well, given the coupling you are showing you are right.

However, if they are coupled as a emitter-follower there will be 2 B-E-voltage drops.

 

By the way: the first controllers I made was made using the coupling you show, but with 3 paralleled output-transistors.

 

Steen

[Greg Erskine]

That's not a darlington circuit is a Sziklai Transistor Pair.

 

Sziklai Transistor Pair Circuit Tutorial (circuitdigest.com)

[smichslot]

I was probably not clear enough: the circuit shown is not a Darlington, and doesn't have a double voltage drop, which was why I made it some years ago.
A Darlington has a double Base-Emitter voltage drop.

Steen

[Greg Erskine]

Hi Steen,

 

Your post was clear to me.

 

I was responding to iv_man previous post, your post must have arrived while I was trying to find out how to spell "Sziklai".   

 

I haven't seen/heard of the Sziklai pair used before for a slot car controller. I did see barnsi simulation circuit here:

 

Transistor controller "Chris Frost" (barnsi.de)

 

regards

Greg

[Greg Erskine]

Well, given the coupling you are showing you are right.

However, if they are coupled as a emitter-follower there will be 2 B-E-voltage drops.

 

By the way: the first controllers I made was made using the coupling you show, but with 3 paralleled output-transistors.

 

Steen

 

 

Hi Steen,

 

How well did the "3 paralleled output-transistors" share the load? Even with matched transistors, I always thought you needed emitter resistors to force load balancing.

 

While emitter resistors are a suitable solution for most circuits, they are not desirable for slot car controllers.

 

regards

Greg

[smichslot]

This is a good question. As you say emitter-resistor cannot be used, and of course its important to find out if the trandistors share the current. It appear that they do. I have testet with low-value resistors (0.005 ohm), and it appear that they share the current.
The reason is that transistors have an "internal" resistance that help them them share the current. The situation is that even if the current is relatively high (3-6 amps pr transistor) the power is relatively low as the voltage is low. No worries!

Steen

[Greg Erskine]

Did you match your transistor pairs or triplets?

 

Maybe 0.005 ohm is enough to force load balancing? Would measuring the die temperatures be possible.

 

I am now wondering if the common practice of emitter resistors was developed when production tolerances where not so tight. For example old 2N3055 transistors probably have a larger differences in specs especially comparing a new one with a forty year old one.

 

regards

Greg

[smichslot]

I don't think that it is needed to match bipolar power-transistors for controller-use. I have repaired several controllers of other brands with no trouble.

 

Today I am using FET-transistors, and here it is absolutly necessary to match them as they have negative G-S-threshold.

 

Steen