4.5v dc power supply

One choice would be a computer power supply's 5 vdc tap with a diode at each building feed to drop the voltage to 4.5 vdc. They are very inexpensive, especially used. I power my Miller signs that way. At 300 to 400 watts, you can power a lot of buildings.

Thanks John

Could I use just one diode to drop the voltage prior to the bus and have a 4.5v bus? What diode would I need?

I’m also told that you can remove the 4.5v board from their buildings and run them direct wired at 3v. Would the diode be able to drop the 5v to 3v or is that too big of a drop?

i apologize for the stupid questions, but it’s new to me and I’m interested in learning how to make it work.

Like John, I use a computer supply cannibalized from dead desktops. Not even sure you need a diode to drop the voltage as long as the 5V is regulated which it is in a computer supply. I know Miller says 5v is OK as long as it doesn't exceed 5V as it does in unregulated supplies. 

Pete

I just found this while you were replying. If the 5v is adjusted to 4.5v, it should have plenty of power - right?

For $20, it seems like a good substitute for multiple wall warts.

Is the board you have on top of a computer power supply homemade or is it sold like shown?

In all honesty we’ve powered menards buildings with a straight 5VDC with no issue. We’re talking about a .5V difference to power lights. If anything else was involved I’d be triple checking everything. But it’s just LEDs that already have individual current limiting resistors. 

Ok, so a 400w computer power supply with the 5v wire feeding a bus seems to be the fix.

i can make my 5.5x2.1 plug wires for the connection to the buildings.

Thanks gents.

@zhubl posted:

In all honesty we’ve powered menards buildings with a straight 5VDC with no issue. We’re talking about a .5V difference to power lights. If anything else was involved I’d be triple checking everything. But it’s just LEDs that already have individual current limiting resistors. 

Usually supplies can be adjusted +/- 10% or so.  I would suggest an inline fuse off the power supply feed terminal "just in case" (OK probably fancy overkill) unless the supply has an internal current limiting foldback circuit, which it probably won't.

A half volt shouldn't cause harm as I can't imagine the buildings being designed explicitly to run on exactly 4.5V, given that in early days these buildings were running on cheapy unregulated supplies, whose output varied all over the place depending on the loadings.

To simplify things, there are adapters that just plug into the power supply's connectors: $8 on Amazon

$18 on Amazon

Thanks John!

Miller sells one that is connected to a transformer.  It outputs 4.5V dc as needed and can power 10 signs.  I have one and it works great.  The price was very low even though I don't recall right now what it was

walt

i should have been a bit clearer.  instead of saying 'to a transformer' better would have been to say 'to YOUR transformer".  it has a wide-range of input voltage allowed.

@Legion JD posted:

 

Without having to make one, is there a good 4.5v dc power supply that will power a dozen or so Menard's buildings?

...

While you undoubtedly mean a dozen "average" buildings, Menards now lists power requirements for their buildings.  Finally!

The point being it should only take a minute or two to do a quick back-of-envelope calculation to estimate your power requirements.  I find the World HQ 5,000 mA somewhat hard to believe, but taken at face-value that's a whopping 22 Watts.   Put a dozen HQ buildings to model Manhatten and you're talking 60 Amps!  Anyway, you get the idea.

Separately, if you review search earlier OGR threads, most guys drive the Menards buildings at less than 4.5V.  Maybe 4V, 3.5V, or even less.  It's personal preference.  If this is of interest, suitable diodes are, say, 10 cents a piece and are an economical way to fine-tune the brightness of a particular building or cluster of buildings.  Each diode drops about 3/4 Volt and you can put multiple diodes in-line (in series) to drop more.

Keep it as simple as possible using any AC toy train transformer use a cheap full wave rectifier as seen here,  Full Wave Rectifier for Converting AC to DC Power .

I picked up several of these at Michael's after Halloween for 75% off. You can light three buildings from each.

To answer a question skipped; General Purpose Rectification Diode(s). Susan's BR is basically four diodes (only two are in use , for a .75v+.75v= aprox 1.5v drop.)   A higher amp diode will stay cooler to the touch than a tiny one fyi (choose over transformer max output or over total LED draw at least).

"Only half a volt" is all it may take to cook an led too LEDs really don't tolerate over voltage well, so basically your hoping ALL the buildings are made with 6v+ diodes -vs- 4.5v diodes (because that is what was available that week at the factory, and could work too )   I'd shoot for under 4.5v .

One advantage I discovered with the computer power supply is that you get superfast circuit protection. I use 24 awg to feed all my accessories, and smaller wire for drops like led street lights or traffic signals. To protect small wire you need a very low amp breaker. I have a 3 amp supplying everything, but the PS trips first in a short.

“General Purpose Rectification Diode”

Can you recommend a higher amp diode from Amazon to drop the volts by .75? 

I’m limited on my parts availability, so I use them for free shipping. 

Legion JD: Look for "diode 1N4003" on Amazon.

Well, the 1N4003 is only good for an amp, if you're doing a larger building or multiple buildings, you might as well step up to at least a 3A diode, they're dirt cheap.

eBay: 173823671460, $1.89 for 10 free shipping from US location.

@Legion JD posted:

..

Can you recommend a higher amp diode from Amazon to drop the volts by .75? 

I’m limited on my parts availability, so I use them for free shipping. 

GRJ's recommendation is for the 1N5408 diode.  You can search on that part on Amazon and there are many choices.  I noticed that some of the Amazon listings with "free shipping" are coming from China which may have you cooling your heels.  There is a reasonably priced diode assortment kit that appears to be fulfilled by Amazon so presumably faster delivery.  It has qty 5 of the 1N5408 (3 Amp) but also includes the 1N5822 (also 3 Amp).  The 1N5822 effects a smaller voltage drop about, say, 1/2 V.  You can mix and match the 1N5408 and 1N5822 to more finely tune the voltage.

That is, if starting from a 5V power source, put one 1N5408 and your output is about 4.25V.  Put two 1N5408 inline and you're down to 3.5V.  That may be too dim.  But if you have 3/4V and 1/2V diodes, you can Lego-style more finely tune the voltage.  Please note that the 3/4V and 1/2V reductions are just for ball-parking.  The actual voltage reduction you will get depends on various factors which can be explored if there's interest...but it does involve graphs and possibly tedious techno-speak.

I still suggest it's in your best interest to inventory the power requirements for your 10 or so buildings...adding up the mA requirements as documented by Menards.  1000mA = 1A.   Even 3A may not be enough!  There are of course higher amp diodes...or you might split your buildings into power districts running on separate 3A diode drops.

Will a 1N1187 in a DO-5 package work to reduce a 5V supply to 4.5V or more?

I think this is rated for 35A and could be used to power the whole buss. Just happen to have one of these.

Probably "or more".

Without getting into the mud about whether these curves apply to DC vs. AC, or the relevance of Tj, etc., look at the vertical axis (Amps).  Approximate how much current you're drawing (note it's a logarithmic scale) and then translate to the linear horizontal axis (Volts).  So for a handful of buildings you're likely in the red-zone so the voltage drop would be about 3/4 Volts.

thanks

For a fairly critical voltage requirement, I'd be tempted to use a regulated power supply and not chintz and use a PC power supply.  I made myself a bench supply with these, they take almost any DC voltage in and output precisely regulated DC power.  Each module is good for 5A DC, and it's a BUCK/BOOST design so you can feed it almost any DC voltage.

Here's the link to my thread on the power supply.

Home Build Bench Power Supply on Steroids

Here's the link to the module above: DC Buck-Boost Power Controller

I gather that powering menard's buildings and miller engineering signs doesn't require critical voltage based on earlier discussions.

I do have a followup question on the diode installation. Does this go in series with the power line from supply or does this get placed between the + and -? Does it matter direction (cathode or anode to the supply side)?

YIKES!  Don't put it across the power supply, you'll simply have a firecracker!

Yes, it does matter which polarity!  It goes in series with the power supply lead.  If you put it in the positive side, put the anode (no stripe) pointing toward the power supply and the cathode (stripe) point toward the load.

I'm no electrician but why are you folks talking about using a diode to reduce volts and amps in your circuits?  Diodes are used to convert AC to DC.....   To reduce Volts and amps you need resistance and that comes from using a resistor.  Or, did I miss the point?

@Kenjr posted:

...Does it matter direction (cathode or anode to the supply side)?

The normal DO-5 package is the so-called "stud-cathode."  This means the cathode is on the stud/threaded side.  So the anode side goes to the +5V source supply side, and the cathode side then goes to the reduced voltage (around 4.25V) load side.

But if you don't know the provenance of your diode, it might be a reverse package style (stud-anode).  However, it should be marked with the (R) suffix.  So it might say 1N1183(R) or something like that.

In any case, if you hook it up backwards you'll just get nothing out on the load side...it will not damage, overheat or whatever.

@Don Dunham posted:

I'm no electrician but why are you folks talking about using a diode to reduce volts and amps in your circuits?  Diodes are used to convert AC to DC.....   To reduce Volts and amps you need resistance and that comes from using a resistor.  Or, did I miss the point?

Well, you did say you're no electrician.

The silicon diode has a fairly fixed voltage drop with a reasonable amount of current flowing through it, here's a typical voltage/current characteristic curve.  Note that the voltage drop remains nearly constant over a wide range of currents.  This makes the diode useful for a known voltage drop over those current ranges.

If you look at a resistor, OTOH, you'll notice as the current goes up, the voltage also goes up in a linear manner.  This is basic Ohm's Law.  This makes the resistor pretty worthless for dropping a set amount of voltage for anything but a fixed current.