Could anyone suggest a digipot with similar function can be used with Arduino (with library)?
The potentiometer used to control output voltage in this power supply is a 10K potentiometer. Can it be replaced with a 100K or 50K digital potentiometer if they are available?
My read is the pot is just a 10K digital pot and the DS3502 seems popular and runs on the I2C bus. A simple Google of ds3502 brings up plenty of hits. DS3502 also brings up libraries. No, you want a 10K pot if you expect decent resolution. Using a 50K will only work for the first 20% of the range and a 100K only 10% of the range.
Likely the pot resistance is not critical but I would get a 10K if I could.
Issues to consider:
You need to find where the pot low side is. If it is at power supply ground you have a better chance of success.
Because the Arduino circuit will be external from the power supply circuitry you may get some electrical noise on the pot command. You may need to add filter caps to the pot wiper output.
Be careful how you setup the wiring. You want to be sure if the digi-pot disconnects the power supply will go to zero not max.
Could you measure the voltage on each end of the pot with respect to the arduino 0V rail?
Ideally with a 'scope, but failing that a voltmeter?
That would tell us if any isolation is needed. If it DOESNT need isolation then as @jhaine suggests I'd just go with disconnecting the pot and feeding the slider connection a suitable voltage.
Hi,
Wouldn't it be easier to leave the power supply at 24V and use a MOSFET to PWM control the current to the heater element.
Use a potentiometer on the input of the Arduino Controller and the output of the controller to PWM the MOSFET.
What are the heater specs/data?
The heat is an induction heater run at max 24V which gives me needed power to heat the device. Since induction heater might be damaged when controlled with PWM or relay, I need to vary voltage instead of turning it on and off.
Also, when PWM is used, thermal couple will be affected by the EMF and a couple of temperature boards have been destroyed. I did shield the thermal couples but still have the problem. PT100 or PT1000 might be good but they cost a lot more. NTC type thermistor and IR sensor have long responding time. Please let me know if you know other method to measure temperature of induction heater.
The needed voltage is up to 24V, it seems MCP41HV51-103e/st coule be used in that voltage range. DS3502 can go up to 15V, which is not enough. Correct me if I am wrong since I am not very familiar with these parts.
If I connect two DS3502 in serial, is it possible to handle 24V since each one could handle 15V. I do not know how to do it yet, but if it is suggested that is possible, I will dig into it. If I do that, the resistance will be 20K instead of 10K.
So you will not be controlling the element directly, but the control circuitry.
Does the induction heater controller/driver have a power level control?
Will the induction heater perform properly with reduced power supply, will the control circuitry like working with reduced voltage?
Can you please post link to data/specs of the induction heater?
What you may want to do here is open the PSU carefully and note how the existing pot is configured. Meaning how is the pot configured in circuit. Your ideal choice would have been a programmable power supply. Measure across the existing pot, hopefully one side is ground. Measure ground to the wiper out. Most programmable supplies used a 0 to 10 volt for 0 to full scale out of the PSU. Hopefully the wiper to ground will be something simple like 0 to 5 volts or 0 to 10 volts.
Not sure how you came up with the 15 volts?
Using a T/C the best way to avoid noise is using a grounded T/C. Since I have no clue what type and configuration what T/C you have it's hard to say much more. Induction heaters are very noisy. What is your temperature range?
The power supply is an adjustable power supply with a built-in potentiometer. It also comes with a connector to connect to an external pot (it actually come with an additional 10K manual pot for remotely change the voltage). I could directly connect the digipot there.
(Amazon.com)
For the DS3502, the datasheet says:
The DS3502 is a 7-bit, nonvolatile (NV) digital potentiometer featuring an output voltage range of up to 15.5V. Programming is accomplished by an I²C-compatible interface, which can operate at speeds of up to 400kHz. External voltages are applied at the RL and RH inputs to define the lowest and highest potentiometer outputs.
Yes, I understand that. The problem is we really do not know what the existing pot is doing in circuit. We can't just assume the voltage out of the existing pot wiper is 0 to 24 VDC. The pot likely only outputs a control voltage. This is why a suggestion is to measure the voltage across the pot, see if one side of the pot is ground and measure the pot's wiper voltage with respect to ground. Need to know is how the existing pot is wired into the circuit. The pot only "controls" the voltage out. I can guarantee you that little pot does not handle the output current.
Matter of fact if the pot wiper just has a simple output voltage with respect to ground like 0 to 5.0 volts you may want to consider a simple I2C DAC rather than a digital pot. Something like this.
