Amp watch

Professorwiz

I've just started using the basic stamp.· I'm currently taking a class but came up with something that could help me out immediatly and was hoping someone did something similar.· I do a little anodizing at home occasionally and you have to hook up a constant current power supply to the leads of the aluminum your anodizing and of course put it in an acid bath.· You have to watch the voltage till it peaks, then when it starts to drop, the part is done with the anodize process and needs to be rinsed.· The amps range depending on the part size and is calculated by the suface area, I usually do around .5 - 2 amp sizes.· Is there a schematic or starting point I can look at to cause a buzzer to beep after it hits the peak.· It usually takes anywhere from 45 min to 1 and 15 minutes it would be great to figure something like this out.

Russ

metron9

What voltage/current are you working with, AC or DC. As you can see i don't know anything about anodizing.

You say you watch the voltage, so that is where you can either connect an analog to digital converter to read the voltage value. Your stamp would then read the voltage and process the information.

If you know the specific voltage point you want to reach you could use a simple comparator. Set it to a voltage point, start the process, wait for the comparator to go high, then wait for it to go low. Use two comparators and set the voltage higher on one, when both are triggered you then wait for the one set at a lower voltage to turn off otherwise at the voltage point you will get many on off signals.

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Professorwiz

The voltage usually starts off at around 8 vdc then ramps up to about 12 vdc for approx 1/2 hour then gradually goes to 16vdc then right around there it drops.· There is no set vdc that it hits and that's the magic number.· It's kinda wishy washy and depends alot of surface finish (rougher finishish gives more suface area than calculated) and such.· So I would have to log say every 5 min. and check the current voltage against the last 5 minutes voltage.· If it was lower then it would have hit the peak and need to be stopped.· What happens is the anodize starts to grow and when it gets to full growth then it hits a peak, after that the acid eats away more than it grows and it gets weird and hazy, and doesn't color right.· It just takes so long that sometimes you get tired of watching the little glowing numbers and you start thinking..hmm was it higher 5 min ago or was it lower, so I have to write it down on a little notecard.. very tedious.·

Tracy Allen

Well, first of all you will need a circuit to read the voltage. It does not have to have much absolute accuracy as you are mainly interested in relative vaues.

There are several ways to measure voltage with the Stamp, but maybe the one described here www.emesys.com/BS2rct.htm#B_voltage would work for this, without requiring another chip.

The program for this will execute a loop to read the voltage repeatedly, and look for the decrease in voltage that will sound the alarm. The trick will be to avoid false alarms due to short term fluctuations. A running average with enough samples could take care of that. It could print out vaues or draw a graph on your computer screen for inspection.

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Tracy Allen
www.emesystems.com

metron9

Here is a hardware solution for you. Its a simple peak detector type circuit. The capacitor holds the maximum voltage minus the voltage drop across the two diodes. About a volt less than the voltage input depending on the diode you use. Use an op amp with unity gain or a comparator to signal when the voltage drops below the highest stored value in the capacitor. You did not say how fast it drops but if it is a long time use a larger capacitor. The pushbutton switch is there to discharge the capacitor. Before you turn the voltage on, discharge the capacitor.

Connect a transistor to the output of the comparator to drive a buzzer or light.

Omit one diode to make the voltage gap 1/2 of add diodes to increase the buffer zone.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Post Edited (metron9) : 4/2/2007 5:53:57 AM GMT