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Electronic expert, pls come in...
- Thread starter EeeK
- Start date
- Joined
- Nov 13, 2001
- Location
- Chicago.
That is still wired for 12v usage. To make it 7v, plug the ground fan cable into the 5v molex cable (red one). To make it 5v, plug the red fan cable into the 5v molex cable (red one).
You can either get a 3 way switch and wire it for 12v and 7v, or you can get a DC Rheostat, also.
You can either get a 3 way switch and wire it for 12v and 7v, or you can get a DC Rheostat, also.
- Joined
- Nov 24, 2001
- Location
- Stillwater, Oklahoma
screw doing a volt mod that is a pain if you want to reverse it....
get one of these. http://www.sidewindercomputers.com/rheosformc.html
get one of these. http://www.sidewindercomputers.com/rheosformc.html
That would 7 volt it.
The middle connection (illustrated with white molex to white molex) demonstrates his crossing the +5volt to the 12volts ground line while maintaining the 12volt line, which would mean that he would get +12 on 12 volt line and +5 on the ground line, thereby 7 volting it.
Note: If **** blows up catches fire or anything else happens. I am not responsible.
The middle connection (illustrated with white molex to white molex) demonstrates his crossing the +5volt to the 12volts ground line while maintaining the 12volt line, which would mean that he would get +12 on 12 volt line and +5 on the ground line, thereby 7 volting it.
Note: If **** blows up catches fire or anything else happens. I am not responsible.
The mod of connecting +12V through a load and other end of load connected to +5V is totally harmless under the following circumstances:
1. The +5V line and +12V line GND is the same.
2. The consumption on +5V line must be bigger (in amps) than the +12V -> +5V consumption.
If these demand 2. isn't met, you'll be forcing current BACKWARDS through whatever is feeding the +5V line. That could spell disaster.
I would hesitate ALOT to try a 7V mod on a unloaded PS, since the only load would be the +12V -> +5V, and NO load +5V -> Gnd.
If one has a, say, 1A load on the +5V -> GND, then it is totally ok to use 0,99 A load from +12V -> +5V.
All you are doing effectivily is take a load of the regulation for the +5V.
Well, thats my "two volts".. errhm.. I mean my "2 cents" !!
1. The +5V line and +12V line GND is the same.
2. The consumption on +5V line must be bigger (in amps) than the +12V -> +5V consumption.
If these demand 2. isn't met, you'll be forcing current BACKWARDS through whatever is feeding the +5V line. That could spell disaster.
I would hesitate ALOT to try a 7V mod on a unloaded PS, since the only load would be the +12V -> +5V, and NO load +5V -> Gnd.
If one has a, say, 1A load on the +5V -> GND, then it is totally ok to use 0,99 A load from +12V -> +5V.
All you are doing effectivily is take a load of the regulation for the +5V.
Well, thats my "two volts".. errhm.. I mean my "2 cents" !!
I think he was confused by your diagram. It's not too hard to read... but it's certainly not standard, so at first glance hell I had no idea what you were doing.
Paxmax. I'm very interested with what you're saying. I'm not very familiar with the behavior of electricity besides it hurts when I stick a penny in the outlet,. So, If I'm running a a 7volt modded fan that consumes say .50amps on an otherwise unused power supply Im forcing 2.5 watts back down the +5 volt line? If unused what does this do? Bump up the power supplies +5volt wattage 2.5watts out of spec and risk overloading it?
Paxmax. I'm very interested with what you're saying. I'm not very familiar with the behavior of electricity besides it hurts when I stick a penny in the outlet,
. So, If I'm running a a 7volt modded fan that consumes say .50amps on an otherwise unused power supply Im forcing 2.5 watts back down the +5 volt line? If unused what does this do? Bump up the power supplies +5volt wattage 2.5watts out of spec and risk overloading it?
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- Thread Starter
- #9
Ok I plannin to make one of these.
Pardon my electronic knowledge, hmmm how does it work? I read the website and it say can connect 2 fans? I thought this have 2 molex connector, one female molex to the fan and the other male molex connector to the powersupply.
I have this fan, delta model FFB0812EHE
Can someone work out for me the spec on which reheostat should I use?
- Thread Starter
- #10
Ok, I've done some calculation. Pls comment.
fan spec: 12 volts, 1.35 amps
therefore r = 12/1.35 = 8.9 ohms
power = (1.35*1.35)/8.9 = 20 watts
Using the formula from Since87 at this thread
Prheo-max = 2/4 = 0.5 watts
Vfan-min = 12*(12/1.35)/(0.5+(12/1.35)) = 12*8.9/(0.5+8.9) = 106.8/9.4 = 11.4 volts
so my ideal rheo would be: 125% of 0.5 = 0.625 watts
???
Did I go wrong anywhere?
PS: when buyin a rheo, what spec do I need to give?
fan spec: 12 volts, 1.35 amps
therefore r = 12/1.35 = 8.9 ohms
power = (1.35*1.35)/8.9 = 20 watts
Using the formula from Since87 at this thread
Prheo-max = 2/4 = 0.5 watts
Vfan-min = 12*(12/1.35)/(0.5+(12/1.35)) = 12*8.9/(0.5+8.9) = 106.8/9.4 = 11.4 volts
so my ideal rheo would be: 125% of 0.5 = 0.625 watts
???
Did I go wrong anywhere?
PS: when buyin a rheo, what spec do I need to give?
- Joined
- Nov 24, 2001
- Location
- Stillwater, Oklahoma
the rheostat is a 5 watt rheostat...this means i can regulate 5 watts of power given to the fan...
this is a good idea because turning it all the way down doesnt mean the fan will be off..it will just be quieter
i have this same one..and it brings it from a high loud/tolerable speed, to a quiet/effective speed....i recommend it to everyone
this is a good idea because turning it all the way down doesnt mean the fan will be off..it will just be quieter
i have this same one..and it brings it from a high loud/tolerable speed, to a quiet/effective speed....i recommend it to everyone
