DC power supply

  • Thread starter freetuc
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  • #1
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Hi. Does anyone knows about a DC power supply that can switch between forward bias and reverse bias automatically? For example, I start it with forward bias, after 1 minute, it will automatically switch to reverse bias, and after another 1 minute, it will automatically switch to forward bias again and keep repeating.

I am looking for this type of power supply for my research purpose. However, I don't really know which type of power supply could provide this function and how am I suppose to search it in internet?

Looking forwards to your kindly assistance.
Thank you so much.
 

Answers and Replies

  • #2
berkeman
Mentor
58,178
8,234
Hi. Does anyone knows about a DC power supply that can switch between forward bias and reverse bias automatically? For example, I start it with forward bias, after 1 minute, it will automatically switch to reverse bias, and after another 1 minute, it will automatically switch to forward bias again and keep repeating.

I am looking for this type of power supply for my research purpose. However, I don't really know which type of power supply could provide this function and how am I suppose to search it in internet?

Looking forwards to your kindly assistance.
Thank you so much.
Welcome to the PF.

So you want +5V output for a minute, and then -5V output for a minute, and so on?

You can use some signal generators to switch at fairly low rates, but I think the lowest I've seen is about 0.1Hz (switch ever 10 seconds or so).

You can make a simple counter circuit to flip a relay to invert the connections to the power supply, if that would work. Is your load isolated from ground?
 
  • #3
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Hi, Berkeman. Thanks for your information. I drew out my research work in the file attached. First, I will start my work as part A where the sample is connected to negative terminal and platinum electrode is connected to positive terminal, and after 3 minutes, I will reverse their connections as in part B. Again after 3 minutes, I will reverse back the connections as in part A and keep repeating.

My problem is that it takes a short time for me to reverse the connections manually and this will influence my experimental result. With that, I wish to purchase a DC power supply that can automatically switches the voltage for me and then I no need to reverse the connections manually. Do you have any idea about this type of power supply?

Thanks a lot.
 

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  • #4
uart
Science Advisor
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Just run the output of your power supply through a mosfet H-bridge and drive it from a timer or signal generator.
 
  • #5
berkeman
Mentor
58,178
8,234
Hi, Berkeman. Thanks for your information. I drew out my research work in the file attached. First, I will start my work as part A where the sample is connected to negative terminal and platinum electrode is connected to positive terminal, and after 3 minutes, I will reverse their connections as in part B. Again after 3 minutes, I will reverse back the connections as in part A and keep repeating.

My problem is that it takes a short time for me to reverse the connections manually and this will influence my experimental result. With that, I wish to purchase a DC power supply that can automatically switches the voltage for me and then I no need to reverse the connections manually. Do you have any idea about this type of power supply?

Thanks a lot.
I googled power supply bipolar programmable, and got a number of hits of standard power supplies that you could program to do what you want:

http://www.google.com/search?tbm=is...bipolar+programmable&gbv=2&aq=f&aqi=&aql=&oq=

But they look pretty big and expensive, so unless you have a big budget for new lab equipment, you may want to take uart's suggestion. :smile:
 
  • #6
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1
Use a double-pull double-throw (DPST) relay (or you could make o with 2 SPDTs) controlled by a timing circuit. How much current / voltage does your experiment need?

On one of the relays poles, hook the positive of your supply to the normally open (N.O.) contact and the negative to the normally closed (N.C.). On the other pole, do the exact opposite (- on N.O. and + on N.C.). The "middle" contacts (don't know the precise term for it, someone else fill it in please!) go out to power your experiment, which seems to be electroplating or electrolysis of some kind.

With the relay unenergized, the voltage will be one polarity. When the relay is energized, the polarity switches.

For the timing circuit, use a http://ca.mouser.com/Semiconductors/Integrated-Circuits-ICs/Clock-Timer-ICs-Analog/Timers-Support-Products/_/N-6j749?P=1yzt4ccZ1z0yhhsZ1z0yz4qZ1z0k084Z1z0z44dZ1z0z7v3Z1z0yz09&Keyword=555&Ns=Pricing|0&FS=True" [Broken] and use the most significant output (Q12) to control the relay. Using Q12 will divide the clock frequency by 212 (4,096),and let you run the 555 timer at a higher frequency.

For example, to switch every 3 minutes, that's a period of 6 minutes for the full cycle (360 seconds). Which the frequency divider, you can make the timer work at a manageable 11.3 Hz, instead of the impossible 2.78 mHz.

The CD4040 doesn't have enough output current to drive a relay coil, so you'll need a transistor of some kind (BJT or MOSFET) to control enough current. I can post a more complete schematic if you need, I'll just have to draw it up.

EDIT: uart's H-bridge suggestion is functionally the same as my relay setup, so you can use whichever is cheaper.
 
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  • #7
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Hello freetuc (is the tuc chocolate biscuits?) and welcome to Physics Forums.

Take a walk (that's good for you) down to your local model railway shop. I bet you will find something that will meet your needs.
Model railways use all sorts of reversing power supplies and timers.

go well
 
  • #8
6
0
Just run the output of your power supply through a mosfet H-bridge and drive it from a timer or signal generator.
Thanks for your information. :smile:
 
  • #9
6
0
  • #10
6
0
Use a double-pull double-throw (DPST) relay (or you could make o with 2 SPDTs) controlled by a timing circuit. How much current / voltage does your experiment need?

On one of the relays poles, hook the positive of your supply to the normally open (N.O.) contact and the negative to the normally closed (N.C.). On the other pole, do the exact opposite (- on N.O. and + on N.C.). The "middle" contacts (don't know the precise term for it, someone else fill it in please!) go out to power your experiment, which seems to be electroplating or electrolysis of some kind.

With the relay unenergized, the voltage will be one polarity. When the relay is energized, the polarity switches.

For the timing circuit, use a http://ca.mouser.com/Semiconductors/Integrated-Circuits-ICs/Clock-Timer-ICs-Analog/Timers-Support-Products/_/N-6j749?P=1yzt4ccZ1z0yhhsZ1z0yz4qZ1z0k084Z1z0z44dZ1z0z7v3Z1z0yz09&Keyword=555&Ns=Pricing|0&FS=True" [Broken] and use the most significant output (Q12) to control the relay. Using Q12 will divide the clock frequency by 212 (4,096),and let you run the 555 timer at a higher frequency.

For example, to switch every 3 minutes, that's a period of 6 minutes for the full cycle (360 seconds). Which the frequency divider, you can make the timer work at a manageable 11.3 Hz, instead of the impossible 2.78 mHz.

The CD4040 doesn't have enough output current to drive a relay coil, so you'll need a transistor of some kind (BJT or MOSFET) to control enough current. I can post a more complete schematic if you need, I'll just have to draw it up.

EDIT: uart's H-bridge suggestion is functionally the same as my relay setup, so you can use whichever is cheaper.
Hi. My experiment need 3V for the voltage. I am not from the electrical background, so I am not really understand about your method. Could you please draw the complete schematic to me? Thanks a lot. :smile:
 
Last edited by a moderator:
  • #11
6
0
Hello freetuc (is the tuc chocolate biscuits?) and welcome to Physics Forums.

Take a walk (that's good for you) down to your local model railway shop. I bet you will find something that will meet your needs.
Model railways use all sorts of reversing power supplies and timers.

go well
Hi. Thanks for your information. :smile:
 

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