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grnsky

Power supply question for Midibox from SmashTV

7 posts in this topic

Hi! Thanks to this forum, I have completed the stuffing of my CORE and DIN from Smash TV. But I'm a little confused about the power supply. I read the Connections Table on this site: http://www.avishowtech.com/mbhp/mbhp_coreR4d.html

It says "Either the output of a 7V-10V transformer, or a wall adapter can be used. 500 mA is recommented, especially if a backlit display is used".

1. How do I determine whether I want to go higher or lower within that range of 7V-10V?

2. After I have my power adapter, do I just solder the adapter right to J1 like it says and that's it? Obviously I'll want to put a socket and on/off switch in between, but I mean, do I need the +/- of the power to touch anything else on the board or just J1?

3. If I have no LCD, do I just check it all out with a multimeter and if all is right, assume it's good to go for the software stage?

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1. Either will work. I personally am a big fan of 9V PSUs as they are incredibly easy to find.

2. Yes, to J1 only. And pretty please use a socket and switch ;)

3. Yes.

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Great answers, thank you! One more thing...how do I figure out what kind of fuse I need. There's nothing about that on Smash Tv website since it's probably more of an optional thing, but I've ready it's a very good idea. Any suggestions? Does it depend on the size of the PSU? Where do I buy one and do I put it before/after the on-off switch?

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fuse? as long as you don t have a maxi MBLC with lots of LCDs and motorfader you may skip the fuse thing.

Otherwise you just need to calcultate how much current you are drawing example:

(some random numbers here)

lcd= 200mA

core=50mA

i/o chain= 200mA

tot= 450mA

let s make it in power= 450mA x 5v =2250mW

let s calculate current for 220volts (europe): 2250mW/220v = 10mA

Take it double, you need a 20mA fuse!

The fuse should go between switch and main

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I should point out too that a fuse is good for testing (accidental shorts, that sort of thing). In fact, you could use a few if you're building your own PSU. They're generally cheap, and can save your components (and/or your transformer).

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While m00dawg is correct and fuses are a good thing - have you ever seen a fuse in a 9V powered device? ;) Just saying... You definitely want fuses when you're working with mains.

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Haha well good point. If you're using a wall-wart then it's hard to use a fuse on the main-side of the transformer. I always went without but I also broke at least 2 wallwarts and a C64 PSU supply (I'm sure it's a fuse, but I'm not going in through all that epoxy to find out :). I guess my point is to be a little more careful when dealing with a non-fused supply.

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