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#1
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Variable current power supply
is there a way of making a variable current supply with an output anywhere
form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks |
#2
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Variable current power supply
Hi Daniel,
An adjustable voltage regulator like the LM317 can be configured for current or voltage regulation. The LM317 wastes 'up to' 3 volts each and outputs 1.5 amps. The LM1086 wastes up to 1.3 volts and will deliver 1.5 amps, the LM1084 will deliver 5 amps. You can configuring one as a current limiter and a second as a voltage regulator to get what you want. You will also need a rectifier (bridge, half or full wave), a couple capacitors and maybe a choke to get the DC to start with.. NOTE: Nothing is 100% efficient. Every component wastes some current and voltage. You will not get 'the maximum of the transformer'. Jay ---------------------------------------------------------------------------- "I'm pullin' for you; we're all in this together", Red Green ---------------------------------------------------------------------------- .. .. "daniel" wrote in message ... is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks |
#3
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Variable current power supply
National LM317 or similar regulator can be used. Data sheet below
http://www.national.com/pf/LM/LM317.html http://cache.national.com/ds/LM/LM117.pdf Look on page 16 for a 1 amp current regulator circuit. Page 17 and 19 have similar circuits for lower current. The "precision" circuit on p17 shows how to make it adjustable. Remember that your load current flows through the variable resistor, so make sure it has high enough power rating. These circuits all assume that the load resistance is low enough that it takes less than (Vin - Vdrop of Regulator - Vref ) volts across the load to get the desired current. The LM317 needs about a 3V drop, and has a 1.2V Reference voltage (which is dropped across the resistor). That leaves you about 7.8V available at the load. Lower dropout regulators are available, and most data sheets will show similar circuits. Wilson "daniel" wrote in message ... is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks |
#4
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Variable current power supply
daniel wrote:
is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks Hi, Thats a theoretical impossiblility. The only way to make a supply with a specific current is by letting the voltage vary. You cant both specify the voltage and current with anything but the R=E/I (resistive) load value. Luhan |
#5
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Variable current power supply
I think you are confused.
What are you trying to do here. Geoff. "happyhobit" wrote in message ... Hi Daniel, An adjustable voltage regulator like the LM317 can be configured for current or voltage regulation. The LM317 wastes 'up to' 3 volts each and outputs 1.5 amps. The LM1086 wastes up to 1.3 volts and will deliver 1.5 amps, the LM1084 will deliver 5 amps. You can configuring one as a current limiter and a second as a voltage regulator to get what you want. You will also need a rectifier (bridge, half or full wave), a couple capacitors and maybe a choke to get the DC to start with.. NOTE: Nothing is 100% efficient. Every component wastes some current and voltage. You will not get 'the maximum of the transformer'. Jay -------------------------------------------------------------------------- -- "I'm pullin' for you; we're all in this together", Red Green -------------------------------------------------------------------------- -- . . "daniel" wrote in message ... is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks |
#6
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Variable current power supply
Well, I was proposing a 'Voltage Regulated, Current Limited' power supply.
Basically two LM317's, one configured as a 'current limiter' and the other as a 'voltage regulator'. O.K.? Jay -- .. ---------------------------------------------------------------------------- "I'm pullin' for you; we're all in this together", Red Green ---------------------------------------------------------------------------- .. .. "Geoff Hackett" wrote in message ... I think you are confused. What are you trying to do here. Geoff. "happyhobit" wrote in message ... Hi Daniel, An adjustable voltage regulator like the LM317 can be configured for current or voltage regulation. The LM317 wastes 'up to' 3 volts each and outputs 1.5 amps. The LM1086 wastes up to 1.3 volts and will deliver 1.5 amps, the LM1084 will deliver 5 amps. You can configuring one as a current limiter and a second as a voltage regulator to get what you want. You will also need a rectifier (bridge, half or full wave), a couple capacitors and maybe a choke to get the DC to start with.. NOTE: Nothing is 100% efficient. Every component wastes some current and voltage. You will not get 'the maximum of the transformer'. Jay -------------------------------------------------------------------------- -- "I'm pullin' for you; we're all in this together", Red Green -------------------------------------------------------------------------- -- . . "daniel" wrote in message ... is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks |
#7
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Variable current power supply
I sugest you use de L200. It's an voltage and current regulator. Wich opperates from 2,6 to 36V and has an max current of 1.5 De application schematics will help you to complete the job On Fri, 24 Oct 2003 01:52:14 -0700, Luhan Monat wrote: daniel wrote: is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks Hi, Thats a theoretical impossiblility. The only way to make a supply with a specific current is by letting the voltage vary. You cant both specify the voltage and current with anything but the R=E/I (resistive) load value. Luhan |
#8
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Variable current power supply
Sorry happyhobit I was referring to the original post from Danial, (where
has he gone), your idea's are fine. The post from Luhan Monat is right however, It is not possible to have variable current at a fixed voltage with a fixed load. When a current sense network kicks in it must reduce the voltage into the load, (at least for DC.) Or for a variable voltage the current must change. The circuit can also incorporate some form of tripping device that requires resetting in the event or a fault, or this can happen automatically.A indication of the degree current limit applied is useful also. I still am not sure what you are trying to do? Geoff Hackett. wrote in message ... I sugest you use de L200. It's an voltage and current regulator. Wich opperates from 2,6 to 36V and has an max current of 1.5 De application schematics will help you to complete the job On Fri, 24 Oct 2003 01:52:14 -0700, Luhan Monat wrote: daniel wrote: is there a way of making a variable current supply with an output anywhere form 0.1A to the maximum of the transformer but using a fixed voltage e.g 12V. thanks Hi, Thats a theoretical impossiblility. The only way to make a supply with a specific current is by letting the voltage vary. You cant both specify the voltage and current with anything but the R=E/I (resistive) load value. Luhan |
#9
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Variable current power supply
i have a 30V AC to AC transformer which has an output current of 2A and i am
trying to get a lower current output around 0.5A which can be adjusted to a greater current like 1.5 or 2A |
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