4.2.4 power requirements


 
P

Paul Hunt

New member
I have two questions regarding power for the HeaterMeter:

Situation: I have a larger blower to drive a UDS, with specified current required 520mA.

Question 1. Will the HeaterMeter onboard FET be adequate for this, or should I use another device? I checked the specs for the BS170, and saw that ID for the device is 500mA continuous, and 1200mA pulsed.

Question 2. Using this blower, what would be an acceptable current rating for the 12VDC supply?

Any advice is appreciated!

Cheers, Paul
 
If I remember the schematic correctly.. The BS170 is just the signal amp that drives the FQU11P06TU, that can do 9.4 amps cont. but I wouldn't push it that hard since there is not a lot of heat sink on the board. But I would guess 3 to 4 amps would be fine... What can your 12volt adaptor supply? ;-)
 
I don't have a supply yet.

I wasn't entirely sure how much juice the Pi + HM board would draw, and also how much current the HM board could source for the fan.

I had only taken a quick peep at the schematic and misread it as the 170 driving the fan. :o

My blower is 20cfm. I might go for 1.5 amp and see how it goes.
 
I've had the 1A PS from the HM BOM brown out on me running a blower around that size, so I would recommend that you go larger, the cost difference is negligible between 1A and 2A PS...
 
I have been using the same 28cfm delta blower since version 2 of the heatermeter and 1.2amp linksys wall adapter without any issues. 1 amp or less brownouts. 1.2amps is perfectly fine.
 
John Bostwick said:
I have been using the same 28cfm delta blower since version 2 of the heatermeter and 1.2amp linksys wall adapter without any issues. 1 amp or less brownouts. 1.2amps is perfectly fine.
Click to expand...

My only caution I would add to that statement is there's a lot of really cheap/crappy electronics out there these days and maybe a cheapo chinese 1.2A ps might not hold as steady as the one Linksys was willing to put their name on.

On the purchase side of the equation, if you buy a 1-1.2A ps and it browns out on you now you are buying a SECOND ps. Since the cost of a 1A PS and 2A PS are virtually the same why not just get the 2A PS? Beyond the blower, if you ever intend to run a servo that's gonna draw more juice so why not have it there for when you need it?

Just my 2 cents
 
Thanks everyone. I am inclined to over-specify (within reason) rather than under. I'll see what I can source (or build) in the 1.5 to 2.0 amp range.
 
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