I bought a USB safety meter. You plug this in first, then you put the ASIC in that thing. Typically, the ASIC runs around 4.8-5.0 V, and 1.8-2.0 AMPS. So, gets me the 9W-10W.
Ah, cool. I have a few of those on order because they're neat, but I'm comfortable with a multimeter and oscilloscope. For reference, your stick, or USB device is running at about 9-10 watts. The ASICs are the two BM1384 chips that lie under the heatsink. While your stick is being supplied with about 5 volts, there's a nifty voltage regulator on the stick that supplies a much lower voltage to the ASIC chips. The ASIC chips run from about 0.650 volts up to (in my experience) 0.8050 volts, and this supply voltage is determined by the setting of the variable resistor (or trimpot) near the USB connector.
I bought the USB safety meter so I wouldn't have to do it. I tried once with a multimeter, but didn't understand how to measure the voltage correctly.
That's easily fixed, and I can walk you through it if you like. This picture shows you where to measure the ASIC voltage.
https://ip.bitcointalk.org/?u=http%3A%2F%2Fi.imgur.com%2F3k4llxx.jpg&t=582&c=uImuQQqhyMCxIQYou set you multimeter to voltage DC range. Then you apply one probe to one side a capacitor, and the other probe to the other side of the capacitor. Depending on the position of the trimpot, you will get a voltage reading between 0.650 volts and ~0.8 volts. This is the voltage being supplied to the ASIC chip. Because there are two ASIC chips, and each has a capacitor, you can measure the ASIC chip voltages independently.
sidehack has built a very tolerant device, and I have been pushing it to absurd limits beyond its design spec, and it has not died on me yet. At first you'll feel nervous putting multimeter probes on a delicate device, but if my particular brand of idiocy hasn't fried the 2pac, then I can reassure you that you don't need to be too worried about hurting it with your multimeter.
Each 2pac stick will have slightly different characteristics. With a 25 degree ambient temperature, my 2pac stick will run with an ASIC voltage of 0.732 volts at 325 MHz. When the ambient temp goes above 26°C I start to have issues.
The idea is to run each ASIC at the minimum voltage at which the stick doesn't fail (and report ZOMBIE) or generate hardware errors. The lower the voltage, the less heat you have to shed with the heatsink. However you can only go so low with the voltage before the stick will begin to experience hardware errors.
I have attached an enormous heatsink to my 2pac, which lets me run at very high voltage without the chip getting too hot, but right now I'm experimenting with just how low a voltage I can run and still achieve stable operation.
Yes. With one ASIC, the fan seems to keep it cool and running fine without intervention for 4+ days.
Good. From the current your stick is consuming and what sidehack has said, I think you can run your ASIC chips at a lower voltage. But before you try this you need to get comfortable with measuring each ASIC chip's supply voltage with your multimeter. Your 2pac stick is being supplied with about 5 volts and 2 amps, but each ASIC chip on the PCB is supplied with a lower voltage. In your position I'd make it my job to get comfortable with measuring and recording the individual ASIC voltage. From there you'll be able to twiddle the voltage down to reduce the power consumption, and reduce temperatures without sacrificing stability.
That's a good point about ambient temp changes. Maybe I need to get a digital thermometer that can record historically.
It wouldn't hurt, but you can just write down the ambient temp when you notice a failure.
I'm confused. Mine for voltage is 4-5 volts. I guess I'm confused why you said 0.73V?
I hope I've explained this above. If I have been clear enough, let me know and I'll take some pictures that show measuring the ASIC voltage. The 2Pac stick needs a 5 volt supply, but it has a really nice voltage regulator that supplies each ASIC chip with a lower voltage.
you got a point and shoot surface temp gun? how much are those? Maybe I should try positioning the hub, so the ASIC is "standing up" versus on its side.
I use stick-on NTC thermistors, but I hear good things about the banggood and HobbyKing IR point and shoot temp guns. Between 15 and 20 bucks ought to do it.
https://hobbyking.com/en_us/catalogsearch/result/?erp_category=&q=thermometer
