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The plot shows up and down ramps which are straight. Is it essential for them to be straight? Because it would not be hard to devise a capacitor charge-and-discharge circuit, with curved ramps.
He can generate voltage linear ramps by charging/discharging a capacitor using a constant current source.
Zeyad, what kind of load do you have in mind? I find quite hard to imagine the utility of such a circuit.
You could do this using a microcontroller (provide the timing), a DAC (controlled by the microcontroller to approximate the ramps by small steps) and a voltage controlled current source from 0 to 50mA, but it's not an easy design for a beginner.
You should be very careful if you decide to build the circuit. 50mA is a current potentially deadly for a human. Also, if you are not going to use some batteries or rechargeable batteries, there are some stringent conditions for any (medical) device connected to the power point. Probably double insulation transformers, I am not sure, but you definitely should check the requirements.
Your desired current of 50 mA through the human body could be lethal. As little as 1 mA through our body can affect the heart, or at least cause a sensation that would alarm most people.
That is a good reason to be careful how high a supply voltage you use, and how much current you send to the transistor bias.
It is also possible to use a mosfet. This would permit you to use a capacitor with a lower value. The resistor network would need to be tailored to provide desired operation.
The table which you showed us contains general information with experiments with two electrodes held firmly in hands by the subjects and for limited (short) amount of time.
The device DC Stimulator contains a lot of protection circuitry, as they say. If imperfect contact appears between skin and electrodes, significant burning can occur. Also note what is the highest current their device is set to deliver: 5000uA which is only 5mA with the comments that typically only currents under 2mA are used.
Also, device is producing constant current, while Bradtherad's suggested circuit is not a real constant current source, therefore improper for this task.
Dear Nick,
if you look to attached patent, you will find the current is up to 10 mA and even more but it is changeable
the device i am would like to design is using electrodes
hi Nick
thanks for your help
i would like to ask of how can i control this output current by audio.
what i mean, i would like to connect an audio voice and would like the current to change corresponding to the audio voice with same frequency
it that possible to design it.
many thanks again, very similar to this diagram
Are you talking about the same project? Initially you mentioned a DC current with specific slopes and a maximum plateau value. Now you are asking about a circuitry that provides an AC current that changes with the same frequency as the voice. They are totally different. For the second circuit, I suppose you could use some sort of audio amplifier and connect your human subject instead of the speaker. On the final amplifiers you would need a constant current source (rather than a standard constant voltage source) that limits the current to a safe value. The final transistors would have to withstand a few hundred volts and the constant current source should have a maximum voltage also of a few hundred volts, but at low current, of course.
hi BradtheRad
thanks for you advice about the circuit
i wonder is it possible to reduce the max current to 2 mA DC output using 9 V souce battery?
i found this diagram but i can't get 2 mA output and i don't know the problem
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