will this work
i need help in designing electric circuit for chemical reaction
the required components are
DC voltage ( i must control it so that i can see the reaction response to different voltages ) in range from zero to 2.5 volt (the main power in my work is AC 110-220 V)
current density in range from Zero to 0.2 Amp/cm2 (also i must control it so that i can see the response of the reactin to different current densities )
thanks too much for any help
thanks alot for reply but how much is it?
i hope it is not so expensive because i need it only for that purpose and after that no need for it
it looks so expensive to me ,iam sorry but if you can help me with samller portale one or simple preliminary circuit like transformer , diode and compose them together
many thanks again for your reply
Grandpa always told us young-ens that if we can’t pay the fiddler stay off the dance floor. Is this the case here?
no it is not the case here but just want to find the alternative when Expenses are limited
thanks again sir for your time and advice
also what make me say that some one told me some thing about constructing circuit using transformer 3 Volt , varying resistance , diode and wires but i cant got it completely and didn't know the arrangement of its components did you understand me ????
I can help you design something. I need to know the area of your electrodes so that I can convert your current density into just a current.
Do you need to be able to adjust current and volts at the same time or can they be seperate? If you don't have to adjust both, it might be easier to do two circuits:
Circuit 1: voltage source that goes from 0 - 2.5v
Circuit 2: current source that goes from 0 - x.x mA
Are you doing hydrogen/oxygen out of water or something else? If you are doing hydrogen/oxygen out of water (and even if you are not), this is a very common experiment and you might also be able to find some good ideas online as well.
thank you sir too much
i want to avoid Hydrogen evolution at first
also i want to adjust both current density and voltage together
the area of electrodes are th internal torch battery carbon electrode area (A battery )
thanks alot again for your time
I'm sure you are a future einstein who will probably discover the theory of dark, or something. IF you don't blow up your daddy's house in the present experiment!
Seriously, you need to find a mentor at school who undertands the electric part of this and can advise you accordingly. It is not quite enough to simply say "transformer...diode...etc"
i need the above circiut i described above in an experiment and The case ended
do you know the conditions !!!!!!!!!!!!!!
finally what i write about diode and transformer not from my own knowledge but electrical engineer who told me that
I understand what you mean on that part. He is telling you how to convert from the AC to DC. Normally, to get DC, you do this:
AC --> Transformer --> rectifier (can be built with 4 diodes) --> capacitor (for smoothing the waves).
This gives an unregulated DC supply. If the transformer is say 12v, then the output would be a bit under 12v (change due to diodes). However, since it is not regulated, if the AC voltage changes a bit, the output will also change.
To fix this, you can do like above and then add a voltage regulator at the end (5v, 12v, etc.) The input voltage from the transformer has to be higher than the regulated voltage. For instance, if you wanted 12v out, then you might need 16v at the transformer.
A cheap/easy way to deal with this part of the circuit is with a computer power supply (from a desktop). These are cheap and easy to find used. They have regulated 5v, 12v, and -12v output and are able to provide a good amount of current. This is what I would use as a starting point for your circuit.
Maybe you can explain the experiment better or perhaps you can give we what the current (not current density) is. Also, how accurate do the values need to be? What I mean is this: say you want 2.5v, does it have to be 2.500v (almost exact) or can it be around 2.5v (say between 2.45v and 2.55v)?
How precise things need to be make a big difference on how the circuit is made. I assume that you don't need things that exact. When you run the experiment, you can use a digital volt/amp meter to see what the values are actually getting.
Controlling the volts and current make things a little more complicated, but it can be done. If you only needed to control voltage, all you would need is the computer power supply, a fixed resistor, and an adjustable resistor. It is about the easiest circuit that can be made (called a voltage divider). It won't work for you since you need to adjust the current too.
Anyway, give me as much information as you can about what you need and I'll see what I can come up with.
In his original post he asks for help with a generator that he can control both voltage and current and know the amount of both.
In order to do this he will need some pretty precise adjustments as well as a display for each. I donít think this is something that someone without some formal training is going to be able to accomplish without spending some money. The Generator I posted is ready for the job at hand. One does not have to buy the unit and can rent one for as long as it is needed,
He is best off using a multimeter to display the volts/current. You would have a very hard time matching what even a cheap DMM can do on your own. If he needed something more compact/portable, he could work it into the design.
I don't think that the actual output needs to be all that precise. Normally, in an experiment, you'll adjust one thing at a time and see the outcome as you change the input. For instance, say you wanted to look at the hydrogen generation rate by placing a DC current through water and looking at what the rate is for different current levels. Say your current supply can do 0-10A. Maybe you'll break up that range into 10 or 20 points. 1A, 2A, etc. The actual current in each step doesn't matter much as you can choose your steps to be whatever size you wish. The important thing is to record the actual current (say it was 0.95A instead of 1A). Then plot hydrogen generation rate vs. current and fit a line through it. Then you have an equation where you could put a different current in and estimate the generation rate.
Since you normally control one thing at a time, that is why I asked about doing two circuits (one to sweep the voltage, one to sweep the current). Do two separate experiments. The voltage source is easy and the current source is easy. One circuit to do both is a bit harder.
Another option is an adjustable power supply (basically like what you show, but more basic/cheaper). Something like this:
1-if you have chemical back ground i will electrolyse aqueous acidic solution in which i dont need the hydrogen to evolve with me ok!!!! thats first
2-this would achieved using carbon electrode (internal graphite in A battery )
3- this electrode would be of high hydrogen over potential to prevent the evoultion of hydrogen
4- the best conditions to aciece the abone conditions are as follows
voltage v current density Amp/Cm2 efficiency of reaction (%)
1.5 0.017 60
1.6 0.024 61
1.7 0.055 63
1.8 0.076 67
1.9 0.147 80
2.0 0.247 61
2.1 0.846 23
2.2 1.456 15
from the above data you can see how i really need it precise as the efficiency decrease from 80 to 61 by increasing the voltage by 0.1 v !!!!!!!!!
but if it went like what you noticified 0.05 increments so it may work i think !!!!!
Last edited by aeacfm; 07-13-2010 at 02:53 PM.