Hello, for an investigation I am using an Arduino Uno WIFI r4 to log the voltage of a 10-20kV circuit. This is for an investigation into EHD thrusters. I am using a voltage divider with an R1 that is equal to 40,880,000 ohms and the R2 is equal to 10,000 ohms. The A1 input is between R1 and R2 and ground is connected after R2. I am using along pins and the value read which is then put trough the formula voltage = value * (5.0/1024)*((R1 + R2)/R2). I am running into the problem that using the Arduino Uno the voltage that it is logging is in the range of 350V. This should not happen because the circuit is discharged and when I add a contact across R2 the voltage goes to zero. I had not ran into this issue when I was using an Arduino Micro. However the Micro is unable to log to the cloud which is why I am using the Uno. Is there any way to solve this issue.
The voltage divider is designed so the voltage of the analog pin will be below 5v. What I was trying to say was that when the circuit was completely offline so 0V across the total circuit of R1 and R2 the Arduino is displaying a voltage of 350V across R2 even though in reality the voltage should be 0V because the circuit is completely discharged, and the Micro showed this. The Arduino Uno only states that the voltage across R2 is 0V when R2 = 0 ohms. Also during testing at voltages which I calculated to be ~11030.4V the Arduino only states 900V.
350V is 1.75% of 20kV. Likely you just have a small offset resulting in the ADC reading 2-3 counts while it should be zero. Since your full scale is 20kV, a tiny offset error translates to a fairly big voltage.
Solving offset errors involves in first instance proper circuit and physical layout. Let's see a schematic of your project as well as some photos of the actual setup. Keep in mind that as long as everything is on a breadboard and experimental dangling wire setup, you're probably not going to be able to entirely solve any offset problems.
Test your setup first with a simple pot meter to 5V and ensure you can accurately read this. Then use a voltage divider to divide down e.g. 12V to a 5V scale and see if you can manage that. Once all that works reliably, go back to the 20kV situation.
wrong
it is voltage = value * (5.0/1024)/((R1 + R2)/R2)
or voltage = value * 19.98533724340176; // 1023 is equivalent of 20445V
we suppose 5V power supply and 1023 max ADC units
350V are 18 units, maybe it comes from ether. you may want detect if voltage is really applied and showing result only if it is really there.
First off, at kind of voltages, the resistors need to handle the voltage level with correct distances. Second, the circuit need to handle voltage spike transients, that occour. I would suggest using clamping diodes for this. If not, you blow your analog input. Third, the uno have 1024 counts, where 0 is used. So you need to use 0-1023 in your code.. Fourth, you need to take into consideration, the input impedance of the analog circuit, when using this kind of voltage dividers. Fifth - you need a voltage reference for the HV side.
Sorry for the late reply. I try to be reasonably safe. I have been dealing with voltages in the range of 10kV for the last year but that was on a developmental set up restricted to a maximum of 60W but only operated at 5W. The current circuit operates at 8.4W and this includes an inverter. I will try to do some low voltage testing to work out some of the problems in the circuit and code.
This image was during the initial set up phase. I am still setting up a more permanent testing area because this was just done in my dining room. Also if anything seems a bit sketch I know, I am only in high school so I only can work on it for about 5 - 10 hours a week, and I am fully paying for this project so I cannot afford for a permanent set up at this point.
This is an image of the High voltage power supply for the EHD thruster (ION engine) It is rated for 1000W at 17.2 kV. I am currently not using this system until I have guaranteed operation on the 8.4W set up.
And I have also confirmed that the Arduino when no charge is applied the arduino is measuring 16 - 20 units. Thanks for helping me.
Thanks for helping me, I will re-design the circuit to include clamping diodes when I switch to the high power system because at this stage I am limited on time to get information, so I have accepted to put the analog systems at risk because so far there has been no spikes in any of my measurements over the course of 20 minutes of testing. I will follow what you said and add Clamping diodes to the high power system because spikes will be more likely, I will also increase the rating on the resistors. I have put 5 resistors for R1 in series over the distance of 20cm and there is only 1 resistor in R2. would you be able to give be the methods for A finding the impedance of the analog system because I know the impedance of the rest of the circuit. B would you also be able to suggest a way to create a reference to the high voltage side. Thanks. Sorry if I have some knowledge gaps because this is one of the first times I am asking for help everything else was self taught.
This contraption should not be allowed to exist, let alone in a high school.
Sorry, I see no way to sugar coat this. This is so woefully inadequate in just about every way for the kind of voltages you're planning to work with...
Maybe @Tordens can give some pointes on HV safety - if he feels comfortable going beyond the obvious "walk away while you still have a pulse".
Your setup looks dangerous. I`m surprised that your teacher let you do this. I do not know what your HV source is. If the HV DC supply can supply some mA, and you touch it, your heart will stop, as long as you touch. Your arm muscles also freeze, so you cant get away easy. Hopefully, your hearth is healty, and may start again if you get away. Many sad videos of this, on youtube.
It seems like you want to make an ionic thruster, like many DIY on youtube. I work with this daily and I can say, this form for propulsion is a dead end in any practial form. What you actually create, is an ozone generator. Ozone is very reactive, with a sweet smell and is very harmfull for creatures, cancerous.
I do not want to take away your effort or entusiasm, as I`m very happy about smart creative people that actually do something in real life, and dont wastw their time on videogames or drugs. So I hope you give it some thougts and maybe lead you into new ideas or tracks.
Thanks for your feedback. I had only tested the abomination that was the high power supply each only being 2s long. I was also located 5m away remotely operating and had clamp meters and multimeters telling me what was going on. During the prototyping phase of the ion engine with currents of 60μA and never touched the circuit until it was discharged. On the point of ozone I 100% agree on the point that ion engines in earths atmosphere are just generators because the original design produced noticeable airspeed but because in the equation
When I increased the number of electrodes the thrust dramatically decreased. I was only able to tell that it was working due to the noticeable ozone smell. The decreased in thrust was why I wanted a higher power circuit. I had known about the issues of sufficient thrust because one like NASA’s AEPS - HERMeS only produced 5N at nearly 200kW and that was not even atmospheric. Ion engines have a very good specific impulse meaning high efficiency but not much thrust. I was also surprised when I first suggested the idea and my teachers were fine with it. If it makes you feel better I will put a pause on the project because today and tomorrow were the last days of testing so I will stop testing out of the interest of safety. I may go back into it later when I have more funding, time and knowledge. I have exams in 4 weeks anyway and currently only getting 5 hours sleep because of the amount of work that I am doing. So it will probably be best to pause it until I can do it more safely and from a better approach or just focus on improving interplanetary travel because that is what I want to work on in the future.
Thanks for trying to help me and looking out for my safety.
