Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Harbor Freight digital scale - need help
Magpie
lab constructor
*****




Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: Chemistry: the subtle science.

[*] posted on 16-8-2014 at 13:20
Harbor Freight digital scale - need help


I just bought the digital scale shown in the following link:

http://www.harborfreight.com/digital-scale-95364.html

I bought it to monitor the weight gain of a gas/liquid reaction as it progresses. With a capacity of 5 kg and a resolution of 1g it should workout well for this purpose. However, the scale automatically shuts off after 40 seconds of operation. I need to somehow override this function. Does anyone have any idea how I can do this? All suggestions are appreciated.

[Edited on 16-8-2014 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
WGTR
International Hazard
*****




Posts: 943
Registered: 29-9-2013
Location: Online
Member Is Offline

Mood: Outline

[*] posted on 16-8-2014 at 14:19


It may be built into the programming of the controller.

My kitchen scale stays on as long as the weight changes periodically. Otherwise it shuts off too. Sometimes they are smart enough to not zero-out if they turn off with something on the scale, but not always.

I suppose that the manufacturer thinks they are doing you a favor by prolonging battery life.
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: Chemistry: the subtle science.

[*] posted on 16-8-2014 at 14:33


Yes, this scale seems to time-out with or without a load, changing or not. If the timer is built into the software then I suppose I'm screwed. There are what looks to be two capacitors (or transistors) wired to the circuit board. But I don't know if they are related to the timer or not. My knowledge of electronics is very limited.



The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
ScienceSquirrel
Super Moderator
*******




Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline

Mood: Dogs are pets but cats are little furry humans with four feet and self determination! :(

[*] posted on 16-8-2014 at 14:52


I have a digital scale that I use for brewing.
It turns off after a few minutes on batteries but when on mains adapter power it chugs on.
Smart scale!
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: Chemistry: the subtle science.

[*] posted on 16-8-2014 at 15:25


I wasn't so sure about it turning off when under a changing load so tested it again just using finger pressure. It stayed on! So it looks like I'll be OK after all.



The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
careysub
International Hazard
*****




Posts: 1339
Registered: 4-8-2014
Location: Coastal Sage Scrub Biome
Member Is Offline

Mood: Lowest quantum state

[*] posted on 16-8-2014 at 16:57


Quote: Originally posted by Magpie  
I just bought the digital scale shown in the following link:

http://www.harborfreight.com/digital-scale-95364.html

I bought it to monitor the weight gain of a gas/liquid reaction as it progresses. With a capacity of 5 kg and a resolution of 1g it should workout well for this purpose. However, the scale automatically shuts off after 40 seconds of operation. I need to somehow override this function. Does anyone have any idea how I can do this? All suggestions are appreciated.

[Edited on 16-8-2014 by Magpie]


The HF scales are inexpensive, and readily available most places - but they are problematic for lab work. They are better than nothing, and can serve as a back-up but there are a number of limitations.

One issue I find is that they do not like you to keep adding stuff incrementally, at some point they decide you must be done and quit registering more mass - or else become "sticky". I have found the need to be alert for an addition not registering when you expect it should, thus indicating you've reached the end and need to reweigh. (And don't short cut and add directly to mixture on the scale, unmixing proves difficult).

They are what they are.
View user's profile View All Posts By User
Magpie
lab constructor
*****




Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline

Mood: Chemistry: the subtle science.

[*] posted on 16-8-2014 at 17:31


I have an Ohaus triple beam mechanical scale that I use for everyday weighing for my experiments. I expect it will outlast me while giving no problems. This HF scale will only be used for special purposes such as the one I described above.

I have bought a number of HF tools. They are OK for occasional use while being much cheaper than quality tools.

I would still like to disable that pesky shut-off timer. So if anybody knows how to do that please tell.


[Edited on 17-8-2014 by Magpie]

[Edited on 17-8-2014 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
View user's profile View All Posts By User
kt5000
Hazard to Others
***




Posts: 133
Registered: 27-3-2013
Location: Southwest US
Member Is Offline

Mood: Final exams

[*] posted on 16-8-2014 at 23:32



I have a similar scale purchased online. Cheap and fairly accurate, but it also times out. If I press the "On" button periodically, it won't time out. I suppose I could rig a circuit trigger that constantly. Maybe even shorting that switch would do it.
View user's profile View All Posts By User

  Go To Top