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Car Power Supply (modified 0 times) tritron Profile I am traying to make power supply for my web player DC DC based on MAX787 5V 5A I am getting 4.99 V and the green lights e-mail and power are on but does not switch to only power light and no boot. What is wrong? 08-06-2002 20:42:37

RE:Car Power Supply (modified 0 times) zmoz Profile The webplayer won't boot untill it has 5.1 or 5.2 volts...I can't remember which... 08-06-2002 20:58:14

RE:Car Power Supply (modified 0 times) tritron Profile Any way to increase it to 5.1 V ? 08-06-2002 21:47:02

RE:Car Power Supply (modified 0 times) simba Profile As per "knarf" the webplayer needs 5.2V to boot up. For using the webplayer from a 12 V system he suggests using the MAX724 and changing R1 in the circuit on the spec sheet to 3K to get 5.2V. If you look at the MAX787 spec sheet you may find a formulae for calculating the output voltage versus some resistor value in the circuit. I have gathered together all of the parts for the MAX724 solution and hope to solder it together soon. I'll let you know how it goes. see http://www.unternet.org/~frank/projects/webplayer/ruggedized/ for more info. 08-11-2002 19:49:36

RE:Car Power Supply (modified 0 times) tritron Profile What is R1 what value it has now ? 08-12-2002 09:42:41

RE:Car Power Supply (modified 0 times) ChocoNutDancer Profile | Email you can get this 5.3V car adapter from CompGeeks for $2 and change the plug to fit the WebPlayer. I just ordered one today. I have a power inverter in the car so I don't really need it but I was placing an order anyway and figured for $2 it would be handy to have on hand in case I wanted to plug it in directly. http://www.compgeeks.com/details.asp?invtid=CADPMP3 I *think* the radio shack plug size I bought for the WP for powering it from a PC power supply was 4.75mm OD and 1.7mm ID. someone please verify this if you get one. 08-12-2002 15:55:21

RE:Car Power Supply (modified 0 times) simba Profile Triton, For the Max724; R1 (resistor #1 in the circuit diagram) for 5 volts output is 2.8K ohms. As per "knarf" changing R1 in the circuit to 3K ohms gets you 5.2V. I don't know it this will be the same for the MAX787 that you mention that you said you are using. ChocoNutDancer, The CompGeeks adapter sounds like a great way to go if it can supply enough amps. My webplayer is modified with a hard drive and cdrom so I may need as much as 5 amps, I am not sure. Let us know if the adapter does OK and what additional loads (hard drive, fan, etc) you have added to your WP. Another thread quotes the plug at 5.5mm O.D., 2.5mm I.D. Radio Shack part 274-1573; I have not verified that info. Let's keep this thread going as I want to get this power supply thing finalized to use my WP for MP3 player, mapping program, etc computer for the car on roadtrips. 08-12-2002 19:21:02

RE:Car Power Supply (modified 0 times) DSPTECH11 Profile I have been messing around with this also and have found that my power supply puts out closer to 5.5V when not connected to the Webplayer. I have increased the resistor value at R1 until I was able to boot into Windows successfully. This is over 3k ohms and just over 5.4 volts, less than this and it would lock up every time. I built the circuit on a perf board and used the larger inductor with the mbr745 schottky. Knarf's plans were so vague and lacking in detail (part numbers and values, elco?) that it was very difficult to track down parts. I hope his site is back up soon or if he reads this I hope he could provide a step by step and part numbers for us non-engineer types. I'm just a hack when it comes to electronic circuits. I plan to add an additional inductor(LC-filter?)and double up on the caps. As for now the MAX724 gets super hot and I'm not sure if it's because of a flaw in my layout. On Knarf's site he claimed that the MAX724 ran cool. I'm trying to draw up a layout to use for etching a pcb for a cleaner layout and signal integrity. Anyone know of a good free design package with an updated and robust library? 08-12-2002 22:53:41

RE:Car Power Supply (modified 0 times) ChocoNutDancer Profile | Email Simba, I'm not sure of the plug size. I might be confusing it with the plug I bought for an LCD display I bought to play around with. what did you do to get the cdrom working? I tried attaching and external desktop cdrom drive that was externally powered. I couldn't get the cdrom drive to work at all. the WP would just hang during boot. I can attach an externally powered desktop hard drive fine though. I picked up a couple of laptop cdrom drives on ebay to experiment with but they both have some strange connector on them and I haven't messed with them yet. I was wondering if some bios's support cdrom drives and some do not. if that was the case then I might be able to flash the bios to another version to get cdrom support. anyone have any thoughts on that? 08-13-2002 11:59:06

RE:Car Power Supply (modified 0 times) tritron Profile I added 300 ohms to sense circuit and that increased the voltage to 5.28V but the webplayer will turn on but no boot or it will turn on and off do I need biger capacitors ? 08-15-2002 23:02:25

RE:Car Power Supply (modified 0 times) DSPTECH11 Profile I added 300 ohms to sense circuit and that increased the voltage to 5.28V but the webplayer will turn on but no boot or it will turn on and off do I need biger capacitors ? I wrote this above... I have been messing around with this also and have found that my power supply puts out closer to 5.5V when not connected to the Webplayer. I have increased the resistor value at R1 until I was able to boot into Windows successfully. This is over 3k ohms and just over 5.4 volts, less than this and it would lock up every time. Check your power supply voltage when it's not plugged in to the WebPlayer and you'll see that voltage is closer to 5.5 volts. I was having the same problem as you until I got the voltage up to 5.4 volts. It still has issues but I'm working on a PCB layout that might clean up output ripple. I also added a 5k pot to adjust the resister value. I'll let you know how it turns out. 08-16-2002 20:16:14

RE:Car Power Supply (modified 0 times) tritron Profile It works fine now it was heat so added heatsink and it work great now 08-16-2002 23:02:37

RE:Car Power Supply (modified 0 times) DSPTECH11 Profile How hot does yours get? I'm using a good size heatsink but the MAX724 still runs hot. Also, what did you use for the diode? I bought the Fairchild MBR745 but used a 180uH inductor like Knarf's did instead of the 50uH specified in the data sheet. Maybe this is the cause of the problem. I might not have the MBR745 in the correct orientation. I believe pin one connects to Vsw but I could be wrong. The data sheet shows the circuit but it's confusing. I added a second 5uh inductor and extra 470uF cap (LC Filter) after the main output cap also. Once I have this figured out I will share a circuit drawing that I made so anyone who is interested can etch their own boards. I'll try to include a parts list with source and pricing. 08-17-2002 19:09:17

RE:Car Power Supply (modified 0 times) tritron Profile It is hot I am using MAX787 but that should put out 5 V only I got more so I can boot. If you hook up diode the wrong way it would killed max724 you are using I use 50 in my circuit. I am using 3300 and 1000 capacitor 3300 for in voltage and 1000 for the voltage out. I used the info from this webpage http://www.edu.kauhajoki.fi/~juhasa/pw/power.html 08-17-2002 22:53:10

RE:Car Power Supply (modified 0 times) DSPTECH11 Profile I'm surprised that the MAX787 is working for you. I had originally ordered them but than I came across knarf's article and ordered the MAX724. I swapped out the 180uH inductor for I what I believe is close to 50uH. I did have the diode in the correct orientation. I am using a 5k pot to adjust the resistance at R1 but I need to dial up 5.6 volts to be able to boot all the way into windows. I'm a little concerned about this but I ran it for about an hour and a half on battery power this way and It was fine. I used what I thought was a large enough sink but that max724 still gets hot. I added a 12V fan and wired it to the input supply. I guess I'm going to have to add a 7812 for safety or use a larger sink. Oh, and the LC-Filter I set up uses a 10uH and not a 5uH inductor like I stated previously but anything from 2-10uH is fine according to the data sheet I am using 3300 and 1000 capacitor 3300 for in voltage and 1000 for the voltage out. Why are you using such large caps? The data sheets and the schematics on the page you referred to show 22OuF on input and 470uF on output. 08-18-2002 12:50:43

RE:Car Power Supply (modified 0 times) tritron Profile I am using large caps because somone on line made the same power supply for computer and he added them because he could not get the pc to boot with cd-rom hard drive and we need 5A 08-18-2002 18:24:46

RE:Car Power Supply (modified 0 times) stoyan Profile ChocoNutDancer, Did the COMPGEEKS power adapter work? I am considering getting one and replacing the connector as long as it works, of course. Please let us know. Thanks in advance, Stoyan 08-25-2002 07:55:51

RE:Car Power Supply (modified 0 times) ChocoNutDancer Profile | Email the car adapter from compgeeks didn't work. it didn't have enough juice to power it. 09-14-2002 17:11:15

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