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C7042 The Power Thread

43422 Views 157 Replies 49 Participants Last post by  Aidan
Time to look at the C7042 Power Output, this the first of a few posts which will cover, how it performs and compares to a 1.5 C7030 and to an S-H Powerbase.

Follow on posts will cover what's in there, how to improve, and using an aftermarket PSU.

To give you the bottom line first. It is very good indeed.
So straight in with a table of numbers and then some explanation.

So we have here, current taken down the left and then the recovered voltage that a car would see. This is shown for a 1.5 C7030 Powerbase with 2 x PS's then a S-H modified Powerbase with an aftermarket PSU, finally C7042 with a single and then 2 PSU's attached.

The table brings home just how bad a C7030 Powerbase, even at 3 Amps the voltage has dropped to half of what we stated with.
In comparison C7042 even with a single PSU only loses 1 Volt at 2.5 Amps.

You can see how well C7042 with 2 PSU's compares to S-H At 5 Amps S-H has dropped 0.43 Volt which is 3% whereas C7042 has dropped 1.55 Volts which is 12% S-H will of course go on to 20 Amps plus.

This is also a little unfair to C7042 because it still has its EMC chokes fitted, whereas they are removed in the S-H upgrade. More on this in a later post when we look at how C7042 performance can be improved.

The numbers in Red for the C7042 are a bit of a bonus. This shows how well the Powerbase volts hold up before overload cuts in to protect the Powerbase. The Overload takes about 2 seconds to cut in, so should cope well with brief shorts, and with large currents taken at a race start.

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Interesting stuff.

How about the 4-car powerbase (dont know if it has number)?

Drove 3 cars on it yesterday on a 6,2m track with 2 lane changers - and had a lot of power issues. ¨

I have ordered the C7042 now, so its just out of coriousity. Cant wait till its arriving - then hopefully none of my mates will talk down my SSD anymore.........
Here are the numbers on the 4 Car Powerbase, both the original and the improved version with the cooling vents.

As you can see they are all very similar because the are esentially the same, with minor tweeks. The new 4 Car is however more robust because of the addition of heatsinks.

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these readings look like only the serious racer with long layout and multiple lc will need to look for power upgrades.So if all goes well its only a case of upgrading cables and updating ssdc as this will be doing all the software issues.

Also shows just how good the s h mod really is and that this pb deserves a update on the ssdc front.
Very cool sir. I'm especially impressed with the bonus numbers on up to 10 amps. Very curious to see the performance with the chokes removed. Can you briefly explain how the chokes work? Will the unit be able to draw more amps without them or is it likely to be more a voltage per amp improvement?
Interesting to see the results for the 4 car powerbase as that is what I will be upgrading from. Now I really can't wait for the boat from China to arrive!

Thanks Rich!
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I will take a proper look round what's in the Powerbase when I do the Look Inside thread, for the moment let's concentrate on the Power path and where the volts go.

So this is what it looks like. You can see two sets of 4 Mosfets, there being an H Bridge for each lane in Analogue. The relay is used to connect the two pairs together in digital mode, so we are paralleling up the Power stages, which is one of the reasons for the good performance.

Just above you can see the chokes. Four single wound ones in each of the feeds to the track and two bifilar ones between them to get rid of common mode noise. These will have been necessary to meet the EMC regulations.

So now going back to the numbers we see that at 5 Amps we are losing 12.95 - 11.4 Volts, so about 1.6 Volts.

About 1/4 of this, 0.4V is lost in the output chokes and the wiring to the track. Now looking at deadpedal's question, replacing them with wire links and beefing up the track wiring would increase the output voltage at 5 Amps by 0.4 Volt, a usefull gain, the current that could be drawn before overload would however not change.

So where do the rest of the volts go? Well I have measured another 1/4, due to variances in the input voltage, in this case not due to the Power supplies but due to the internal regulators that sit under the heatsink and fan. So replacing the regulators & probably the input resettable fuses with links could give us another 0.4 Volts at 5 Amps. Also at this point we would be able to add a variable aftermarket supply.

The final 0.8 Volts I have not yet measured but will almost certaily be in the RDS on of the mosfets, and is actually a good number.

More detail to follow later when I have a production Powerbase to play with and can try the changes in practice.

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It's nice to see the numbers. They lay out the facts behind what I was seeing in my testing. It takes a LOT of cars to make this PB flinch. I think the overwhelming majority of users will never want for any power upgrades. It blows the original 6 car and the anemic 4 car bases completely out of the water, and holds its own nicely against a Simple-H unit. This base is how it should have been all along.
Now scaley needs a real off-the-shelf fuel management system like the others all have.
YES, I vote for the add-on of fuel management. PLG has sense to me only as Pit-Pro.
Happy to see the new PB is reaallllyyy good!
Credit to Scaley
and Pro guys

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QUOTE (RichG @ 9 Aug 2010, 02:13) <{POST_SNAPBACK}>So straight in with a table of numbers and then some explanation.

You can see how well C7042 with 2 PSU's compares to S-H At 5 Amps S-H has dropped 0.43 Volt which is 3% whereas C7042 has dropped 1.55 Volts which is 12% S-H will of course go on to 20 Amps plus.

Thanks for the starting point.... A few thoughts:

- when comparing S-H and C7042, one must note on the table that the 'starting' (no-load) voltage between the two is not the same. The C7042 starts at around 13v, whereas the S-H starts at around 12.4v If both PSUs were the same higher voltage, then the output from S-H at 5A would be .6v lost to get to something more like 12.9v, while C7042 has lost 1.5v to 11.4
- the RDS of the mosfets seems high - since in digital they are in parallel (when using 2 PSUs) they calculate out as 0.32 ohms split between both top and bottom of each bridge. Many P & N matched TO220 mosfets total less than 0.2 ohms, which makes me wonder about the drive here
- the mosfets are required to dissipate some 4 watts which is quite low for a TO220 device

What are the output part numbers, and how are they driven - is that the 16pin device to their left?

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I appreciate that the starting voltages are different, it's just difficult to contrive them to all be the same, particularily when they are done with different PSU's and at different times. To a first approximation the best thing to do is to look at the delta change in voltage at a common current, and then express as a % change, which is what I have done.

In this case 5 Amps. C7042 sees a 12% reduction, and S-H sees a 3% reduction. I think this is a fair comparison.

To then make it even fairer
if you were to subtract the volt drop in the output chokes from C7042, as they are removed in the S-H upgrade, then the result for C7042 is 9%

I was not saying that the remaining 0.8 Volt was entirely due to RDS ON, just that that was the result of the non accounted for voltage, RDS ON will of course be a chunk of that, however there is likely to be something else I have missed.

The mosfets are FQP20N06L 60V 20A

RDS On is quoted at 0.06 Ohm which at 5 amps should be 0.3V * 2 / 2 for the parallel stages = 0.3V, so yes you are right, much less than the 0.8 V unnacounted for.
However bear in mind my measurements made a bit quickly and I was concentrating on the losses after the Mosfets, and due to the PSU regulation.

Yes the driver chips are the 16 pin devices, much better than the direct drive in C7030. They are ISL83202

More work to be done.

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Critical thing stands, though - output is much better than the old PB6. I also assume a bit of cooling runs off the fan & heatsink to dissipate some of that heat on the mosfets to maintain stability...?

Only N-channel FETs?

More than 1 ISL83202 - where's the other located?

No way is that designed, it may be a "feature"...
Yes there is quite a nice current of air that passes over the mosfets, which is giving some cooling and preventing any hot spots forming. All 8 devices are N-channel Fets, the driver chip enables them to be used on the High & Low side. Yes 2 driver chips you can just see the second one poking out from the LHS of the heatsink.

Thanks for making all this easy to understand Rich!

BTW, I'll be hooking up my after market power supply this evening. Just want to make sure that I get the polarity correct on the Advanced 6 car. Center is positive and outer is earth right? (same as original 6 car?)
These cables found at the link below are working very well with my aftermarket power supply!

I checked the polarity before giving it a go. The red banana plug end matches the red on my Pyramid PX-26KS.

If you happen to not already have any of the Scaley wall warts, aftermarket PSU works great! (and who would pay $120 for wall warts?)
I will combine two cables to hit both outlets shortly... after I stop playing
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That is a very nice and tidy solution.
Deadpedal.......Thanks for the cable link. Ordering two sets today.......
Wow! That's about the best solution ever! You might even be able to plug in the second set through the extra holes in the PSU output, if yours has them (I don't have that model) and not have to do any wire cutting or soldering. And the price is pretty great! That one belongs in the SSD 101 thread. I wonder if anyone has the gumption to start up a new one now that the new base is/will be out soon?
After combining two cables I've got more amps than I know what to do with (for now). Running with several pace cars is very fun and the wife and I ran some analog together for quite a while (well... for as long as I could keep her interested

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