[Barry-TJetSlots]

A few months ago I had asked for advice on using two power supplies and received excellent advice. I ended up using a dual adjustable (voltage and current) power supply and had very good luck. I typically set the voltage for each supply about 21.5 volts and have 3 amp fuses in each line. I've monitored the current on the supply and each supply appears to draw about 150 - 200 mA. In the last couple of months I've increased the track length to about 55 feet. Should I consider increasing the supply voltages above 21.5 volts?
Thanks for any feedback

 

[MrFlippant]

No.
Add power taps.

 

[Barry-TJetSlots]

No.
Add power taps.

Could you describe what is a power tap?

 

[MrFlippant]

It's wire that you connect to a source of power to the track, that you then connect to another part of the track.

Every track join of sectional track introduces resistance in the flow of power. The longer the track, the more resistance, and the poorer the power. Power taps bypass those joins to bring better power to "distant" (by number of track joins, not actual distance) points of the track.

The more power taps, the better. Tracks on which competition takes place usually have the power from the PSU and controllers go to a central point, that then has multiple power taps going to places around the layout to evenly distribute the power.

These are sometimes called "jumpers". There are plenty of guides on line for how to install power taps for any given kind of track. If you google "power taps brand" where "brand" is your kind of track, then I'm sure you'll find what you need.

 

[Barry-TJetSlots]

It's wire that you connect to a source of power to the track, that you then connect to another part of the track.

Every track join of sectional track introduces resistance in the flow of power. The longer the track, the more resistance, and the poorer the power. Power taps bypass those joins to bring better power to "distant" (by number of track joins, not actual distance) points of the track.

The more power taps, the better. Tracks on which competition takes place usually have the power from the PSU and controllers go to a central point, that then has multiple power taps going to places around the layout to evenly distribute the power.

These are sometimes called "jumpers". There are plenty of guides on line for how to install power taps for any given kind of track. If you google "power taps brand" where "brand" is your kind of track, then I'm sure you'll find what you need.

Got it. Essentially we are setting up parallel paths to bypass the impedances for both the hot line and the ground line for each of the lanes. I have a few extra 9" terminal tracks so I'll start at the mid way point to add the first set of jumpers from the original terminal and assess the improvement.

 

[jordan89]

The idea is to eliminate any 'dead spots' on longer tracks by using power taps/jumpers, dead spots are pieces of track where the the continuity is not what it should be so car stutters/engine noise whine will change/lights may dim etc. and you notice a lack of power driving. or worse, car stops...

Even if you don't have any of the symptoms above they're still a good idea to make sure it stays that way.

Take a feed from the track piece that you feed power to and use a star configuration for redundancy to other points on track, you can also feed off them too however they are not redundant.

There are loads of posts here illustrating the concept, doesn't matter what type of track it is, they all require stable voltage around track. A longer track will drop more DC voltage (as said above), due to resistance and the taps help giving consistent power, using thicker wires will also help voltage drop as you have a bigger boat!

If you run analogue then make sure and connect each rail (4 in total) to the same rail when running the taps! If digital only you can get away with just connecting two rails (+ve/-ve to same) as track is now one large digital lane.

Best to solder the taps, however if, for example, you have Scalextric Sport you can use the lugs under track with a 3mm spade connectors if track has to be taken down regularly.

In fact if you're MrF you could even solder every individual track piece together, then, you never need worry about power again (I'm too lazy, my 4 taps do me fine;-) )

 

[jordan89]

Also, get some INOX MX3, the small bottle with the needle applier, this is slot car equivalent of Nitro, a few drops on each braid and run few laps on each lane, instant improvement in continuity, performance and so lap times as well as protecting the rails if not steel ;-)

 

[peregrine]

I have not yet included any power taps to my 94 foot ARC PRO digital layout but have got them and do intend fiting them.
What I find is provided the track has been given a realy good clean up, everything runs realy great but intrduction of any
dust or contaminent and things get rather slow at the more remote parts of the track, from power sauce.
Taps definitly needed!!!.

 

[MrFlippant]

Dead spots are catastrophic loss of power, pretty much a total break from the source of power. I don't talk about "dead spots" because most tracks don't actually have them, but most tracks DO have power drop. This is when the resistance from the joins (sometimes poor, but functional) is such that the car can go, but it has less pep and less brakes. Those still new to the hobby often don't even notice this issue. The more one races, the more these sections of poor power stand out, and the more they feel the need for power taps. This is not an issue of power delivery from the rail to the car through the braids, but an issue of power delivery from rail to rail to rail... This is what power taps/jumpers are meant to mitigate, if not eliminate.

 

[jordan89]

Dust or contaminants shouldn't affect the voltage unless the 'contaminant' is a bottle of beer? .;-)

With Scalextric Sport temperature can be a factor/enemy too, especially sunlight with LCs randomly flipping, heat/cold will expand/contract track by mms which affects the continuity, ask me how I know...

 

[Barry-TJetSlots]

Thanks for the feedback. I added a voltage tap at the mid-point of the layout (see attached). The measured impedance was 0.2 ohms for each of the 4 jumpers. Tested with one of my slower cars and it makes a difference.

 

[RichD]

A better test for voltage drops due to poor connections is to take voltage measurements with a load applied to the circuit. Bad connections act like resistors and the voltage drop across a resistor is proportional to the current going through the circuit. No current means no voltage drop, so unless a section has a complete open on both sides the voltage will look OK. If you punch the controller for one lane and put a car with the rear wheels off of the track on a section you can the measure the actual voltage under load. I like to pick a section that is half way around the track for a start, if that measures very close to what I see where the track power comes in everything in between should be OK as well.
It is best to deal with bad joints before you add jumpers. On a very long track, even with perfect joints, the rails will have enough resistance to cause a voltage drop, especially with high performance cars.
If you have a power supply with an amp control, always leave that turned all the way up.

 

[tlbrace]

Is 21 volts typical for HO layouts?

 

[Barry-TJetSlots]

A better test for voltage drops due to poor connections is to take voltage measurements with a load applied to the circuit. Bad connections act like resistors and the voltage drop across a resistor is proportional to the current going through the circuit. No current means no voltage drop, so unless a section has a complete open on both sides the voltage will look OK. If you punch the controller for one lane and put a car with the rear wheels off of the track on a section you can the measure the actual voltage under load. I like to pick a section that is half way around the track for a start, if that measures very close to what I see where the track power comes in everything in between should be OK as well.
It is best to deal with bad joints before you add jumpers. On a very long track, even with perfect joints, the rails will have enough resistance to cause a voltage drop, especially with high performance cars.
If you have a power supply with an amp control, always leave that turned all the way up.

I like the idea of measuring the voltage under the full load. I did measasure the static voltage just as a quick check. Before adding the power tap, I had already cleaned every track contact and the rails. The tap at the mid point definitely establishes the extra power boost, Attached is a picture of my dual power supply with both voltage and current control. I'll check the voltage midway to the power tap.
Thanks

 

[RichD]

I have never seen a power supply the has two sections that can be switched to be in series or parallel. With an unregulated or undersized power supply the voltage can drop considerably when even a modest load is applied. I tested an old Aurora 20 volt power supply that dropped down to 14.2 volts with a 0.55 amp load. A car with a 6 ohm armature will pull that much when it is accelerating.
Club type HO tracks are run at 18-20 volts, my club uses 18.5 volts for most classes. If you use the latest switchable AFX power supply those are 24 volts at the highest setting.

 

[Barry-TJetSlots]

I have never seen a power supply the has two sections that can be switched to be in series or parallel. With an unregulated or undersized power supply the voltage can drop considerably when even a modest load is applied. I tested an old Aurora 20 volt power supply that dropped down to 14.2 volts with a 0.55 amp load. A car with a 6 ohm armature will pull that much when it is accelerating.
Club type HO tracks are run at 18-20 volts, my club uses 18.5 volts for most classes. If you use the latest switchable AFX power supply those are 24 volts at the highest setting.

This power supply has a 5 amp rating for each supply. Each supply connected individually to each lane. The ammeter on the supply has indicated 150 to 200 mA during load.

 

[X2slotbob]

Of course, the taps need to be connected post controller.

A couple of things to consider:

--DHORC runs very long tracks with no jumpers, as do other clubs that set them up in halls temporarily. (If anyone knows Nick Sismey, please tell him Jay sez "hi")

--IF you have a "bad" connection just after the tap location, the car will still slow or stop.

SO, make sure your connections are good and then see if you have a problem. One easy way to do this is to hold down the controller and listen to the rpm on the terminal track . Now move the car to halfway around the track. Is is the same or less? If less, back it up until it is once again the same. Now move forward on section at a time until you find the point of degradation.

IF it is at one particular point you have a connection problem and I would suggest that NEITHER adding power taps nor more voltage (or amperage, for that matter) will help.

If it just slowly drops, then more amperage and possibly taps will help.

In a related sidebar, I notice that AFX now has "dual terminal tracks" apparently in stock (although I believe that Barry has plenty of power).

Terminal Track - Dual | AFX RACING

1 Track Piece Per Package

afxracing.com

 

[X2slotbob]

"Is 21 volts typical for HO layouts?"--tbrace

As Rich mentions, club tracks are typically run at 18-20 volts.

In my case, 20.5 (on the meter of the power supply) is the most I can run without shortened motor life with my tyco inlines.

 

[RichD]

A power supply with more amp capacity is not a cure for a track with bad joints. I once ran on a ~150 foot Tomy track that had no jumpers and that was fine with regular set type cars.

 

[Mark]

I have a 100ft scaley track and although not confident with soldering I have been listening to Mr Flippant...if a full or half straight doesn't have a spade connector tap wire then it's not doing its job!! Not sure how many taps now but very consistent power. As others said, taps and Inox seems to be the solution.