Large Scale Central

Aristo -9/SD45 with and without QSI

Electronics Power and Sound
#1

For the first time yesterday, I got enough incentive to break out all my six-axled Aristocraft diesels and give them a thorough airing with a reasonable train of around 25 cars. You realise, of course, that such a train reaches about 1/3 round my entire layout, but what the heck.

Heading up with my QSI-equipped BNSF -9 loco, I noticed within seconds of start-up that the second -9 loco, without a sound-system, was spinning its wheels and trying to push the front loco along, so I shut down immediately and had a think about it.

I don’t recall reading anywhere that you can’t run two loco’s in tandem, of which only one is fitted with a sound system, but I think I understand why this is happening.

Incidentally - trying out all nine of the others afterwards on empty track was very interesting - three at a time, they all followed each other around keeping station about three feet apart for as long as I let them run…

Trying out the QSI-fitted loco and a non-fitted loco with space between them - the system-fitted loco had not even begun to move before the other one was going like he** around the track.

Spoils me a bit for trying to run a lash-up with only one loco making noise. Makes fitting one unit in each loco sort of compulsory, too, sadly, for my wallet.

tac
www.ovgrs.org

#2

Dear TAC,

Is your system DC or DCC?

Track power or battery power?

Does the QSI module control the motor in the sound equipped loco?

Thanks.

Joe Satnik

#3

The QSI has a microprocessor, so you need enough voltage to run it before anything else can happen. That’s about 5 volts to the chip, so you should be running at 6-7 volts…

If you think about it, there is no other way, other than running it from a battery all the time, something needs to have voltage first (like constant power).

Regards, Greg

p.s. I believe LGB put diodes in line with the motor in some cases, so enough voltage would build up to run the sound card first, before the motors started moving without sound.

Regards, Greg

#4

Thanks for the replies Guys, and yes, Greg - you’re right and I sort of guessed that would be the way of it. I put a meter across the tracks this afternoon and found that all my other six-axled locos actually began moving at between 2 and 3 volts - a tribute to the quality of motos used by Aristo-Craft in their products.

Since I usually run a lot of visiting locos, my inner track is either DC with control knob or TE or nothing - for steam ops - and the outer track is anything plus MTS. I don’t know anybody who has battery power and any form of RC here.

Thanks again and apologies for repeating my query on another forum.

Tac
www.ovgrs.org

#5

TAC, I read the responses you got on the Aristo forum, uhhh… glad you did not listen to them… that’s all I will say…

One idea, a set of diodes to drop the voltage in the non-QSI loco, with a switch to take them out of circuit… so in circuit, have enough diode drops to make start voltages similar… and out of circuit back to normal…

Should be pretty inexpensive, you use maybe 3 full wave bridge rectifiers… that way it passes both polarities…

Regards, Greg

#6

Greg,

Won’t putting diodes in limit you to running in one direction? I guess the “back to normal” switch would give reverse back, but with the motor running faster.

What about a constant power source to the QSI sound board, say some rechargeable batteries?

Joe

#7

Joe - As Greg suggested, use multiple full wave rectifiers. If you wire it correctly you will end up with diodes in either direction, so both forward and reverse voltage will pass though the diodes giving the voltage drop while maintaining reversibility.

(http://www.faqs.org/docs/electric/Semi/03265.png)

#8

Nice compact way to put 2 diode drops that are polarity insensitive in line with your motor… if you think of the 2 wires on the top and bottom as “inputs” and the 2 wires connected to the resistor as outputs, you tie the inputs together, and the outputs together…

now you have a 2 terminal “device” that can go inline with one of the track leads, or motor leads… and it does 2 diode drops, easiest way to do it, and full wave bridges are inexpensive… string as many of these devices in series as you need to equalize the starting speeds (slow down the non-QSI loco). you can also put a switch in the circuit to bypass this so the non-QSI loco will be “normal”… cheap, easy way to solve your problem.

Regards, Greg

#9

Jon,

Did you create that illustration? Great looking diagram.

Greg,

If I tie a single bridge’s two ~ (ac) terminals together (input), and tie the + and - terminals together(output), I get a polarity insensitive voltage drop, but of only one diode drop worth, as the two conducting diodes are in parallel…

or am I missing something?

Thanks.

Sincerely,

Joe Satnik

#10

Joe Satnik said:
Jon, Did you create that illustration? Great looking diagram. Greg, If I tie a single bridge’s two ~ (ac) terminals together (input), and tie the + and - terminals together(output), I get a polarity insensitive voltage drop, but of only one diode drop worth, as the two conducting diodes are in parallel… or am I missing something? Thanks. Sincerely, Joe Satnik

Connect the bridge as shown. The connect the Pos. & Neg. pins together (+ & -). Connect the two AC pins (~) in series with one of the motor leads. Current will flow from pins 4 to 3 to 1 to 2 in one direction and 4 to 1 to 3 to 2 in the other direction. Total 1.4 volts each direction Your done.

(http://www.lscdata.com/users/dennis_cherry/_forumfiles/Diodedrop.jpg)

If you need another 1.4 Volt drop the just add another diode bridge.

(http://www.lscdata.com/users/dennis_cherry/_forumfiles/2-8V%20Drop.jpg)

#11

Dennis,

Clever. Perfectly clear now. Thanks.

Joe Satnik

#12

Thanks Dennis, I should have drawn the diagram, then I would have realized I said to connect the wrong leads.

Regards, Greg

#13

Dennis,

I went through school learning positive current flow, so I had to think backwards from your (negative current flow or electron current flow) description…

Commander Positron would say “Flow with the arrows, citizens!” (2 to 1, 3 to 4, other direction 4 to 1, 3 to 2.)

Sincerely,

Joe Satnik

Edit: Removed dual bridge circuit comment.

#14
Joe Satnik said:
Dennis,

I went through school learning positive current flow, so I had to think backwards from your (negative current flow or electron current flow) description…

Commander Positron would say “Flow with the arrows, citizens!” (2 to 1, 3 to 4, other direction 4 to 1, 3 to 2.)

Also, you might want to check your dual bridge circuit. I get current flow only with positive track voltage up.

Hope this helps.

Sincerely,

Joe Satnik


Oops: should have checked the 2.8V circuit a little closer.

Thank for pointing it out.

Its fixed now. Blush, Blush

#15

So, is this smoke and mirrors, or PFM?

#16

Just to clarify the current flow of a diode to everyone.

This is a basic tutorial on diode current flow.

http://www.allaboutcircuits.com/vol_3/chpt_3/1.html