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Q-bert controls software asjustment ?
Level42:
--- Quote from: 2600 on June 26, 2006, 02:48:56 pm ---Level42, Datasheet says you can feed 35V into an LM7805, but regulating down to 5V it's going to get hot. The question is do you need to isolate the power? You are isolating the IPAC, do you need to isolate the power or protect it or none of the above?
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Yeah the 35V is an absolute maximum and normaly you would put max about 20V into a 7805. Not needed for isolating, just for lowering the Vbe voltage. However, in theory this can also be done with a simple voltage divider using resistors.
Forgive my persistance, but I want to see if I can learn a little from this too....here's my last attempt, 2600 please review and let me know what you think.
R3 (10k) and R4 (1k) work as the voltage devider. There should be a little less then 3 Volts on Vbe this way. I've lowered R2 to 20k, since the base current will be already running through R3 which is 10k, so 10k+20k is 30k which should give a safe base current.
Although I don't see the need for it, R3 and R4 should also work as pull down resistors as you suggest.
Fire at will !!! If this is all wrong again, I'll stick to Brad's original design :)
2600:
--- Quote from: juggle50 on June 26, 2006, 05:43:57 pm ---Does that mean that I need two diodes? One for the + and one for the - going from the ledwiz to the relay?
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See here.
http://www.kpsec.freeuk.com/components/relay.htm
The diode goes across the +/-.
2600:
--- Quote from: Level42 on June 27, 2006, 12:57:15 pm ---
--- Quote from: 2600 on June 26, 2006, 02:48:56 pm ---Level42, Datasheet says you can feed 35V into an LM7805, but regulating down to 5V it's going to get hot. The question is do you need to isolate the power? You are isolating the IPAC, do you need to isolate the power or protect it or none of the above?
--- End quote ---
Yeah the 35V is an absolute maximum and normaly you would put max about 20V into a 7805. Not needed for isolating, just for lowering the Vbe voltage. However, in theory this can also be done with a simple voltage divider using resistors.
Forgive my persistance, but I want to see if I can learn a little from this too....here's my last attempt, 2600 please review and let me know what you think.
R3 (10k) and R4 (1k) work as the voltage devider. There should be a little less then 3 Volts on Vbe this way. I've lowered R2 to 20k, since the base current will be already running through R3 which is 10k, so 10k+20k is 30k which should give a safe base current.
Although I don't see the need for it, R3 and R4 should also work as pull down resistors as you suggest.
Fire at will !!! If this is all wrong again, I'll stick to Brad's original design :)
--- End quote ---
Sorry, but no. Your problem is trying to use a voltage divider. That's why I asked my original question. Do you have to use the 30V supply? Do you require isolation from your other voltage supply, ie IPAC, PC?
But don't just listen to me, there are a lot of good people here.
Level42:
Well basicaly, that is what introducing the optoisolator was all about. Using the power on the PC/Ledwiz/I-pac side would still couple that with the 30V and the idea was to make an electrical seperation between those.
So then the optoisolator is totaly unneccesary and complicating things and we could better use Brad's original diagram.
Still haven't received the knocker by the way ! :angry: :cry: :banghead: :badmood: :hissy:
2600:
You can use an isolated DC-DC converter powered off the 5v line.