Well, if you've read my thread in the Ps2 section, you know my dilemma. If you haven't, then here it is; I'm making a Ps2p and since the Ps2 runs on 8.5v instead of 7.5 like most systems, I'd need an 8.5v battery. The problem is that the Zenith screen can't handle 8.5v without the daughterboard, which I don't plan on using.
Can the Zenith/Psone screens handle 8.5v? If not, what's the smallest, and most efficient way to step the voltage down to something the screen can handle?
Stepping 8.4v down to 7.4-7.5v
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GonzoMPM-1
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Wow, your problem exists on a couple of levels because a typical drop out regulator is going to lose more than a volt and a half in the stop down, which will leave you below operable levels with the PS1 Screen. (Or put another way, you won't be able to put out 7.5 volts unless you put more than 8.5 volts into the regulator circuit).
Have you considered using a 12 volt power supply and a couple regulators to get to your desired voltage?
Alternatively, Might I suggest you find a large amperage (sufficient for maximum load of the PS2 screen and then some) rated DIODE and use that?
By way of background, silicon diodes present significant voltage loss by operation of the P-N junction. Depending on the diode specs, forward voltage loss (sustained) is usually between .7 and 1.4 volts.
For clean D.C. powered devices (e.g., powered by a battery), you could consider using a diode to reduce power. Its rather crude, but not unheard of especially if there's a small swing between source and desired voltage and current draw of the target device is fairly consistent over all usage conditions.
Edited to add:
One thing I was not very clear on is that this only works if your current draw is fairly consistent. The voltage drop varies with current, which you'll see on a chart for whatever diode(s) you look at. So you really need to monkey with your multimeter and check the current draw of the screen over all conditions, (especially volume up, and the maximum pixel activation at the TFT screen). That will establish a range and then you can consider whether diodes will meet your need.
You know, a 780x isn't an expensive, or, large component.
Have you considered using a 12 volt power supply and a couple regulators to get to your desired voltage?
Alternatively, Might I suggest you find a large amperage (sufficient for maximum load of the PS2 screen and then some) rated DIODE and use that?
By way of background, silicon diodes present significant voltage loss by operation of the P-N junction. Depending on the diode specs, forward voltage loss (sustained) is usually between .7 and 1.4 volts.
For clean D.C. powered devices (e.g., powered by a battery), you could consider using a diode to reduce power. Its rather crude, but not unheard of especially if there's a small swing between source and desired voltage and current draw of the target device is fairly consistent over all usage conditions.
Edited to add:
One thing I was not very clear on is that this only works if your current draw is fairly consistent. The voltage drop varies with current, which you'll see on a chart for whatever diode(s) you look at. So you really need to monkey with your multimeter and check the current draw of the screen over all conditions, (especially volume up, and the maximum pixel activation at the TFT screen). That will establish a range and then you can consider whether diodes will meet your need.
You know, a 780x isn't an expensive, or, large component.
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GonzoMPM-1
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- Joined: Sat Jun 14, 2008 10:56 pm
There is always the Dimension Engineering adjustable regulator. If you don't mind spending the 15 bucks.
http://www.dimensionengineering.com/DE-SWADJ.htm
http://www.dimensionengineering.com/DE-SWADJ.htm
Looks perfect, and small. It's a good thing you showed me this, Ben doesn't like to explain the small things when he's detailing a portable.grahf wrote:There is always the Dimension Engineering adjustable regulator. If you don't mind spending the 15 bucks.
http://www.dimensionengineering.com/DE-SWADJ.htm
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bacteria
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No idea if this would work, might be worth testing?
PSone screen should, from what I read elsewhere, work at 8.5v, however this is close to the maximum, and as I found with my Li-ions, they tend to output more voltage than they claim (7.4v @ 8.3v in my case). You could always use a diode to reduce the voltage to the screen - I think a diode cuts about 0.7v, so 8.5v > about 7.8v; fine for the screen.
No idea if this would work, you could always test it out without connecting up your system, so no damage done.
PSone screen should, from what I read elsewhere, work at 8.5v, however this is close to the maximum, and as I found with my Li-ions, they tend to output more voltage than they claim (7.4v @ 8.3v in my case). You could always use a diode to reduce the voltage to the screen - I think a diode cuts about 0.7v, so 8.5v > about 7.8v; fine for the screen.
No idea if this would work, you could always test it out without connecting up your system, so no damage done.
There's no such thing as an 8.5v battery (closest would be a nickel battery at 8.4v, 7 cell). So say you got an 8.4v battery.
Range from dead to full is on average 7 to 10.5 volts.
Look into switching regulators, a simple diode is not enough to "regulate" voltage.
EDIT: Typical maximum voltage for a PSOne screen is 9v.
EDIT 2: What grahf posted would work, though it's pretty expensive.
Range from dead to full is on average 7 to 10.5 volts.
Look into switching regulators, a simple diode is not enough to "regulate" voltage.
EDIT: Typical maximum voltage for a PSOne screen is 9v.
EDIT 2: What grahf posted would work, though it's pretty expensive.
8v works great with a PSOne screen, no doubt about that; but you need to feed the 7808 about 10v for it to output a decently accurate power line (the regulator would work for ~20 minutes from full charge, then your portable would shut down). Linear regulators such as the 78xx series are not so great for close regulation.jeffslot wrote:I use a 7808 regulator to feed my screens all the time - it seems to work fine.
Use a switching regulator. Search ti.com for free sample parts, or Digikey if you're buying anything else (way expensive to buy just one item).
-Skyler
Is it possible to just use the daughter board? The reason I ask is, I don't feel like defrauding a company to get free samples, and I don't really want to buy a couple hundred of them. And then the fact that I have the daughter board here, and I'd have to wait even longer to really start this thing if I order something else.
