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Post by David Murray on Dec 27, 2004 18:11:43 GMT -5
I'm about to connect external power to my DTV. I read somewhere that it has a poer regulator to bring it down to 3 volts or something. Does that mean I can just use any old wall-wart AC adapter that has an output of 5 Volts? I know 5V goes to the PS/2 port (also about to connect tonight) but I didn't want to risk blowing the innards up if I didn't have a properly regulated adapter.
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Post by NetSamurai on Dec 28, 2004 1:51:57 GMT -5
The linear regulator built in should be able to handle a 5V supply within reasonable specs. The batteries you install put out a little over 6V when fresh. Some unregulated wall warts will put out like 6V and count on the current draw to bring the voltage down. I am fairly certain the DTV could handle this, but I would worry about the keyboard you plug in. A safer solution might be to use a 9V supply and a LM7805 regulator to get a more accurate 5V supply. I would make sure whatever power supply you use, that it can put out at least 500mA. With the keyboard and the IEC plugged in, I believe I measured about 350mA current draw. This was with no activity on the IEC bus.
I am fortunate and had an extra 5V switching power supply meant for a PDA. It is highly regulated, and is capable of cranking out 2-3 amps! Very nice! You can sometimes find these on Ebay pretty cheaply. Mine is for a Toshiba E-series PDA.
Scott McDonnell
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Post by David Murray on Dec 28, 2004 9:49:48 GMT -5
Okay.. that is what I used. I guess we think alike. I found a power supply for a Compaq Ipaq and it puts out 5.09 volts with my meter even with zero load. I finished wiring all my ports.. actually, what I did was find a bunch of female ended cables and made little holes for the cables to come out abou 18 inches (includes IEC, power, and PS/2) and to my amazement everything worked the first time.
One thing that is strange, though. If I turn off the power switch to my DTV the screen goes blank. But when I turn it back on, it hassn't lost its memory. It is still sitting on the screen in the same place it was. Doesn't matter how long it is off. I hooked up the 5 volts right to the main terminals (along with the keyboard) So I'm guessing somehow the power is slightly feeding back through the PS/2 keyboard which is always getting power now (unless I unplg from the wall) and keeping the memory alive in the unit. --DavidM
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Post by 87C751 on Dec 28, 2004 13:34:17 GMT -5
I have a Power-One MAP55 sitting around (+5, +/-12) that's rated for 6A at 5VDC. Think that'll do the job for me?
And for thos of you that used some kind of power plug, got a DigiKey p/n?
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Post by 87C751 on Dec 28, 2004 21:29:52 GMT -5
Strike that. I found a straight 5VDC/2A supply that used to run an ethernet hub. It works well on initial tests.
I decided to go with a 1/8" phone plug for power so I can take advantage of the closed-circuit jack to switch the batteries out of circuit when I plug the PS in. That'll be my first case mod.
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Post by NetSamurai on Dec 28, 2004 22:14:28 GMT -5
I can't give you a part number because it depends on what your power supply already uses for a connector. If you are OK with cutting the plug off the end of your power supply then you can get whatever size you want in a matching jack and plug. 2.1mm and 2.5mm are probably the most common. Whether you want panel mount or PCB mount depends on your application. Here are some suggestions: Plugs Jameco#: 28759 2.1mm Plug with strain relief Jameco#: 138587 2.1mm Plug Right-angle Jacks Jameco#: 151554 2.1mm Panel mount jack Jameco#: 151589 2.1mm Panel mount jack (looks nicer) Jameco#: 137672 2.1mm PCB mount jack www.jameco.com/webapp/wcs/stores/servlet/CategoryDisplay?storeId=10001&catalogId=10001&langId=-1&categoryId=11496Scott McDonnell
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Post by NetSamurai on Dec 28, 2004 22:25:31 GMT -5
David, How do you have the switch wired in there? The effect you are describing sound very strange.
When you are saying the keyboard is always getting power, do you mean that you bypass the switch with the 5V? If the keyboard is on the +5V and ground on the DTV board, it shouldn't be getting any power when you turn off the switch.
I mean it sounds really neat, but I am worried that maybe you are shorting out the 5V supply when you use the switch. In the long term, this won't be a good thing. The PS you are using probably has short-circuit protection built in (since it is for a handheld device) but relying on that for extended lengths of time might pose a fire hazard.
Even with a short, it would still supply a small amount of current which would probably keep the RAM fresh (it is SRAM, not DRAM)
Scott McDonnell
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Post by NetSamurai on Dec 28, 2004 22:36:25 GMT -5
David Murray wrote:
From this statement, I am certain you are shorting out your power supply with the switch. In fact, the switch should be working in reverse now. When you turn it off, the DTV turns on because you removed the short. When you turn it on, it shorts out the PS and the DTV doesn't get enough power to run. Your power supply is supposed to go through the switch in series. You are running it in parallel. While this seems to be working fine with your supply, it is definitely a safety hazard.
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Post by 87C751 on Dec 28, 2004 23:17:10 GMT -5
And the first mod is a success! For the terminally curious, pictures are available at www.rant-central.com/nudge-nudge/MorePowerUPS says my other two will be here tomorrow. Now if digiKey would just hurry up with my DIN connectors...
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Post by Tormentor on Jan 4, 2005 22:55:37 GMT -5
Newbie here, so please be kind. Proud Vic 20 owner here, in fact the Vic is the reason I'm a software developer today. Let me preface my plea for help here by stating that I'm a programmer, not a hardware guy. I can "scratch" build modern PCs since everything is components you just plug together like legos, but my soldering is limited to connecting my car radio, 120vAC lamps/switches/toggles, etc....putting the iron to a circuit board is a tad bit scary...that's why I want to try I'm about to sell my real 64C to free up space, so the DTV sounds like fun to play with. (you'll have to pry my Vic 20 from my cold dead fingers, though). Boy, all the pages are wonderful, but since I'm volts/amps challenged when I'm not connecting prewired plugs, I want to make sure I'm not about to fry or otherwise destroy a DTV (I'm going to buy 2 just in case). Rather than use a bulky PC power supply, I'm looking at a "wall wart" I believe folks have called it. I have a spare from a small receipt printer that is actually rated at output of 5VDC, 2.4A. Most I've seen were for 9V. I see that PC power supplies have the one output in their power connectors that are 5VDC, 18-22A. Most of the wonderful web pages for DTV hacking show the 5V, but what about the 2.4A versus 18 or 22. Will the 2.4 be sufficient to power both the DTV, a PS/2 keyboard I want to add? I tried to add up the batteries to see what the unit wanted with no hacks, but I'm sure confused about what is necessary once you connect a keyboard. Also, I haven't looked yet, but do my proposed DB-9 Male joystick port and 1541 serial port draw any power too? If I have to use a PC power supply, I guess I will look for some scrap micro/flex ATX small form factor barebones box or something, but if I can wire that 2.4Amp wall wart directly into the DTV, I'd much rather do that, and just add all the ports and put the whole thing in a small electronics project box. Also, what about ventilation in a small project box? If I go that route, now am I hosed and in need of a fan? If so, now I'll be missing that 12V line of a PC Power supply, so that may push me back to a larger box hehehe. Anyway, sorry I'm so stupid about amps and volts, but you guys have posted such wonderful, wonderful websites of instructions that I'm just itching to try getting this thing running with a classic Atari joystick DB9 port, PS/2 keyboard, and 1541 cable Thanks for any insight you're willing to dispense to a "soldering" newbie. I need to use rosin solder, right?
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Post by David Murray on Jan 4, 2005 23:30:33 GMT -5
Tormenter.. as I'm the original poster of this question it seem silly for me to answer.. but I've learned much about the device since then. First of all, the number of amps listed on your adapter is not important as long as it is as least around 1 amp (or 1000 miliamps) So far I haven't seen anybody say they've gotten it to run on less than that. I'm using a 2 amp wall-wart on mine and it works great. Nobody has had a straight-forward answer on how high of voltage you can pump into it. The problem is a lot of these cheap wall-wart adapters do not output exactly what they say and are often several volts higher in low-load situations. So measure yours with a volt meter. I was lucky to find one that outputs exactly 5.09 volts even with no load because it was designed for a PDA. Appearently the circuit board has an onboard regulater to reduce the voltage down to like 3 volts or something like that. However, the PS/2 keyboard should be getting fed right around 5 volts. I suppose different brands of keyboards might have different tolerances to higher voltages like 6 or 7 volts.
Even if you mount the DTV in a new case, you shouldn't need a fan to cool it unless something specific about the case or power supply itself requires cooling. Otherwise the DTV board is designed to run pretty cool on its own.
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