Today I made arduino control 30,000 volts.

My arduino has 3 channels of analog output 0 to 5 volt.

For testing I used this sin wave generator sketch:

int pwmPin = 9; // output pin supporting PWM

void setup(){

pinMode(pwmPin, OUTPUT); // sets the pin as output

}

void loop(){

float something = millis() / 1000.0;

int value = 127.5 + 127.5 * sin( something * 2.0 * PI );

analogWrite(pwmPin,value);

}

 

This generates a lazy 2 Hz sin wave.

But the output is not really analog, it’s pulse width modulation(PWM):

This tutorial shows how to smooth out  PWM using a low pass filter. My low pass filter used 6kΩ resistor and 4.7 µF @ 45V capacitor.

Here we have the raw PWM output superimposed with the filtered output:

Looks good!

Now we just add the voltage doubling op-amp circuit I made previously, and BOOM:

This shows the source signal and the voltage doubled signal.

Sweet! Now we can control the 30,000 volt glassman power supply.

Here the arduino is sending a slow sin wave to the glassman’s voltage control:

From 2011-09-10

The Glassman’s slew rate is really slow without a load.

Here is the setup:

All photos.

Yesterday I got the IGBT working under computer control. I switched my desk lamp on and off from my computer. The IGBT will be used to switch up to 90 Amps going into the superconducting magnet.

IGBT

Schematic:

Here is a video of the win:

From 2010-10-07

I’ve been exchanging emails with Raymond R. about the details of voltage suppression. He suggest using TVS diodes to protect each channel of the DAQ from voltage spikes in the wire by clamping them just above  the channel’s operating range.

I’ve ordered these TVS diodes:

1.5KE7.5CA

1.5KE12CA

Raymond suggests the following:

1) Buy the  NI USB-6000 Series Prototyping Accessory if you have the money and want to avoid messiness; otherwise you can kludge the wiring. (I’ve done this).

2) 16 (+ 4,5 spares) of  LCE10A-ND (I bought corresponding parts at mouser).

3) Go to differential mode on NI USB 6008 (good idea).

4) Connect the TVSs from each input/output line to  frame ground.

5) Take the cable shield and do not connect it at the USB board; connect back to the computer frame.  The TVS diodes go to the cable shield not to the USB box grounds.  Connect the USB grounds together and to the shield ground through a 1 meg resistor (alternately a .1 uf ceramic cap).

Got the mass flow controller online!

First we got a +/- 15V power supply on eBay for $30:

Real nice Lambda. 3.3 Amp.

Wire up the AC side:

Solder the pins on the 9 pin Dsub – data cable on the left, power on the right:

The MFC draws 60 mA. The MFC’s pinout:

Physically install the MFC:

This required a female to female VCR fitting seen to the right of the MFC. It’s pretty securely connected with just the VCR. Stuart suggested installing the MFC upside down to reduce the chance of knocking it downward.

Here it is fully installed:

And it works! First try. Here I have adjusted the chamber pressure to even numbers:

When I am running at full flow, the chamber reads 1.9 e-2 torr.

Here is a video:

Details after the jump.

The Sorensen SRL 10-100 allows for remote control of voltage and current. For current control you simply remove the jumper between terminals 7 and 8 and install a resistor to set a current. This model uses 10 ohms per amp – so a 10 ohm resister would set the current to 1 amp. From the manual:

To adapt unit for current mode, resistance programming operation, proceed as follows:

a. Close POWER switch, adjust output voltage to desired compliance setting.

b. Open POWER switch and rotate CURRENT controls fully counter-clockwise.

c. Remove link between terminals TB2—7 and TB2·8, and replace with programming resistor.

CAUTION

Operating unit with open programming leads or links will result in high output current with possible crossover to voltage mode. If ·step changes in output current are to be made by abrupt resistance alterations, use make·before-break switching.

To adapt unit for current mode, resistance programming operation, proceed as follows:

a. Close POWER switch, adjust output voltage to desired compliance setting.

b. Open POWER switch and rotate CURRENT controls fully counter-clockwise.

c. Remove link between terminals TB2—7 and TB2·8, and replace with programming resistor.

CAUTION

Operating unit with open programming leads or links will result in high output current with possible crossover to voltage mode. If ·step changes in output current are to be made by abrupt resistance alterations, use make·before-break switching.

d. Run load to terminals TB3·1 and ‘I‘B3·3, observlng polarity.

e. Set POWER switch to ON. Unit supplies regulated programmed current to the load.

NOTE Any rotatlon of the CURRENT control alters the output current. Dangerous output currents may result. The panel current knobs may be removed lf desired.

So easy enough. But I still need some way to change the resistance from the computer. Enter the digital potentiometer.

This is the specific digital potentiometer chip (MCP4021 – 202E/SN) I used:

Pretty tiny. I had to switch my soldering tip:

Here it is with tiny leads soldered to it:

Very fragile, so I expoxied it to some prototype PCB:

Schematic:

Wired up to the DAQ, and the fluke multimeter set to measure ohms:

Here is an overview of the protocol for wiping the potentiometer:

A 2-wire synchronous serial protocol is used to increment or decrement the digital potentiometer’s wiper terminal. The Increment/Decrement (U/D) protocol utilizes the CS and U/D input pins. Both inputs are tolerant of signals up to 12.5V without damaging the device. The CS pin can differenciate between two high-voltage levels, VIH and VIHH. This enables additional commands without requiring additional input pins. The high-voltage commands (VIHH on the CS pin) are similar to the standard commands, except that they control (enable, disable, …) the state of the non-volatile WiperLock technolgy feature. The simple U/D protocol uses the state of the U/D pin at the falling edge of the CS pin to determine if Increment or Decrement mode is desired. Subsequent rising edges of the U/D pin move the wiper. The wiper value will not underflow or overflow. The new wiper setting can be saved to EEPROM, if desired, by selecting the state of the U/D pin during the rising edge of the CS pin.

So I wrote a small ruby program using the DAQmx library to slowly ramp up and down.

Short circuit the power supply for current mode operation:

Finally hook up the assembly to the power supply:

SUCCESS as you can see from the video at the top of the post!

Voltage reading (via voltage dividers and ammeter shunts); low power voltage reading from magnetometer, thermocouple, pressure gauge, etc; on the output side: voltage control of power supplies, servos for needle valves, triggering IGBTs; Our ion gauge has the option of digital over RS485.

I purchased an NI USB-6008 (manual, driver):

Unfortunately the driver for this does not work with Snow Leopard yet. I’ve already upgraded my main laptop to Snow Leopard and I really don’t want to downgrade to Leopard so I dug up and old G4 running Tiger. Had to swap out a broken CD drive:

This G4 will be a challenge to upgrade to Leopard as it lacks a DVD drive, although it may be possible to install without DVD.

I was able to install the driver NI-DAQmx_Base. I opened up NIdatalogger and performed a successful grab of voltage data on the analog input:

I would like to get this ruby adapter working. So far I can’t get it to build on Tiger (it makes it further on Snow Leopard). I’m working with the creator to get it installed and working:

Last night I attended NYC Resister for the first time… wow. Really impressive. Talented, well equipped, and fun. In 5 hours I went form zero knowledge to a working computer controlled stepper motor using the reprap electrical hardware. I can’t understate how much more productive and fun it is working with like minded individuals. 
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