AD633 simple circuit

Thread Starter

Flierman1945

Joined Feb 1, 2018
3
This is the first time I have ever needed help in my near 60 years in the trade, but perhaps as we grow older, we get more dafty.
I have in the past built an energy harvesting circuit to use on my Solar Panel Install. It is a fairly simple circuit using a single current loop on the incommer tail of my supply. When I export, the unit harvests the generated output minus power uasage into a hot water storage tank. My first unit has been running for near Five years with no problems. So, I thought I would knock up another unit. I built it and after checking everything many times plugged it in. Over the years I have always put the back of the finger on the chips to check temp, this time the AD633 was heating up too fast. I did the usual rechecked the circuit which was fine, bought another chip, popped it in and the same problem. I could not work out what was going wrong. It is same in every respect as my original circuit.
So I decided to buy one last one and put it into a simple test rig circuit. I used a breadboard and my bench power supply and reduced the running supply to +12 and -12dc and o volt gnd. I used a simple circuit on the Anologue Devices pdf, it is the squaring and freq doubling circuit, very simple, Ideal as a test. So armed with another chip I breadboarded the circuit, fed a 50 htz signal to pin 1+3 and grounded pin2+4 nd pin 6. I scoped the input and set it to 10v p to p sine wave in. My bench supply shows current and at swithch on current was 317ma. What I found was even with another new ad633 if I grounded pin 2 or pin4 then the chip drew max current. I left all connections open and just applied +12 volt and -12 volt , no current showing, I then grounded pin 6 and there was a 200 ma drain.
My simple question is"Am I going mad" There is the circuit below. This circuit is published, it is bound to work, so why are my chips burning out???????




ad633.PNG

This is the circuit I have built previously, so I know it works. It is a phase shift measurement circuit j2 is the current transformer looped over the incomming mains tail pin7 of the ad708 delivers a pulsed output when my solar panels are exporting and hence drives the output control of this unit.. Very simple. On the ad633 pin1 is a ac waveform and pin 3 provides a ref ac waveform from the mains when pin 7 goes neg, the o/p pulses drive the ad708. R10 and C10 together provide a dc monitoring voltage which allows trimming of the unit to stop using the harvesting unit when the generation is less then around 100watts .
So can anyone help with my dilema, what can I be doing wrong, perhaps I have bought a batch of duff chips, I just don't know, please dive in with any thoughts.

harvest.PNG
 

Thread Starter

Flierman1945

Joined Feb 1, 2018
3
Where did you purchase the chips?
Is it possible they are fake?
Well, that is a question I thought might pop up, A couple from chipshop on e-bay, not sure if they were sourced from AD, and 4 from China. I know, don't say it. Perhaps I ought to give it one last go and but from RS or Farnell.
 

crutschow

Joined Mar 14, 2008
27,394
Glad you found the problem (albeit at some extra expense).

Electronics from Ebay and China are definitely caveat emptor, particularly for parts that are sole source and somewhat expensive from that source. :rolleyes:
 
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