Help the microcontroller

Thread Starter

stregoi

Joined Jun 12, 2014
9
Hi .. i am new to Electronics, i hope someone can help me.
I am working on a simple countdown timer for a research project. The Timer Counts Down from 2:00 min to 0:00 on a click of a button ( no other buttons ). i already made a working prototype in arduino ( it is the only thing i always has worked well ).
Now i need to make 6 models of the timer for the research project. But i am not sure what is the best microcontroller to choose for this project. the power should be as low as possible as i will use batteries. I only have programmed arduino boards.

Any suggestions ?
Thanks
 

jpanhalt

Joined Jan 18, 2008
7,929
Agreed, any microcontroller can do that. If you use a PIC with TMR1, that timer can work during sleep (low power) and the interrupts will give you your countdown ticks.
 

jpanhalt

Joined Jan 18, 2008
7,929
Also it has to be an MCU with low power consumption (nA) in sleep mode, like a PIC18.
Not really. Since you didn't name a specific chip, it is difficult to be specific; however, many PICs (e.g., the 12F1840) have sleep modes that draw the same or less current than a 18F2455 series for example.
 

ArakelTheDragon

Joined Nov 18, 2016
1,267
Not really. Since you didn't name a specific chip, it is difficult to be specific; however, many PICs (e.g., the 12F1840) have sleep modes that draw the same or less current than a 18F2455 series for example.
Why not really? I said "like a PIC18", not mandatory pick PIC18!
 

Thread Starter

stregoi

Joined Jun 12, 2014
9
Thanks Guys ... To be specific, we are doing a small project to understand if a visual feedback helps surgeons to scrub their hands the right way ( it should be done in 2 min ).
So it is a Countdown timer connected to the handle of the alcohol dispenser. When a surgeon clics on the dispenser, the timer turns on and starts counting Down from 2:00 min to 0:00, when it is done the display is turned off.

So basicly the components are a 3 digits 7 segment display, a button and the chip of course. And it will run on low power.
 

ebeowulf17

Joined Aug 12, 2014
2,942
Thanks Guys ... To be specific, we are doing a small project to understand if a visual feedback helps surgeons to scrub their hands the right way ( it should be done in 2 min ).
So it is a Countdown timer connected to the handle of the alcohol dispenser. When a surgeon clics on the dispenser, the timer turns on and starts counting Down from 2:00 min to 0:00, when it is done the display is turned off.

So basicly the components are a 3 digits 7 segment display, a button and the chip of course. And it will run on low power.
The LED power consumption is going to be so much more than the microcontroller consumption - low power controllers are the least of your worries!
 

jpanhalt

Joined Jan 18, 2008
7,929
The LED power consumption is going to be so much more than the microcontroller consumption - low power controllers are the least of your worries!
I don't recall the TS saying it was an LED display. Maybe he is thinking of a non-backlit LCD as are common in the usual kitchen timers.

Sounds like a hand switch, rather than a foot switch is being contemplated. That might be more of a concern for a surgeon scrubbing. Also, if the switch is hit twice, does it restart the count or continue? Why not just use a clock on the wall or one of the many "jingles" to get an acceptable scrub time between surgeries?

As I recall, there are different scrub times for the first surgery of the day and between surgeries. Will the timer take that into account?
 

ebeowulf17

Joined Aug 12, 2014
2,942
I don't recall the TS saying it was an LED display. Maybe he is thinking of a non-backlit LCD as are common in the usual kitchen timers.

Sounds like a hand switch, rather than a foot switch is being contemplated. That might be more of a concern for a surgeon scrubbing. Also, if the switch is hit twice, does it restart the count or continue? Why not just use a clock on the wall or one of the many "jingles" to get an acceptable scrub time between surgeries?

As I recall, there are different scrub times for the first surgery of the day and between surgeries. Will the timer take that into account?
Oops! I shouldn't make assumptions. Yes, you're right. If it's LCD, not LED, it could be very low power.
 

Thread Starter

stregoi

Joined Jun 12, 2014
9
I don't recall the TS saying it was an LED display. Maybe he is thinking of a non-backlit LCD as are common in the usual kitchen timers.

Sounds like a hand switch, rather than a foot switch is being contemplated. That might be more of a concern for a surgeon scrubbing. Also, if the switch is hit twice, does it restart the count or continue? Why not just use a clock on the wall or one of the many "jingles" to get an acceptable scrub time between surgeries?

As I recall, there are different scrub times for the first surgery of the day and between surgeries. Will the timer take that into account?
- i am using a 3 digits, 7 segment display, not an LCD screen.
- The surgeon will not touch the button it self, as the button is connected to the dispencer it self, and it wont be touched by the surgeon
- The aim of the study, is to see if a countdown timer will help the surgeons to scrub during the whole 2 min, we have a clock on the wall but it does not help.
- The rules in our department is scrubing during 2 min, it does not matter if it is the first surgey or the last one, scrub time is always 2 min.
- when programming the prototype in arduino i took in consideration that the switch is disabled once the timer is started, so it does not matter how many times the surgeon hits the switch. the only things that will reset the timer is the end of the 2 min.
 

Thread Starter

stregoi

Joined Jun 12, 2014
9
Oops! I shouldn't make assumptions. Yes, you're right. If it's LCD, not LED, it could be very low power.
You suggest an LCD display, or OLED in stead of the 3 digit 7 segment display ?
The most important is the power consuption but also the price as i am going to make several devices and it is only a local research project, so founding is limited.
 

ArakelTheDragon

Joined Nov 18, 2016
1,267
yes i will be using a 3 digits, 7 segment display
Its better to use an LCD, unless its for
- i am using a 3 digits, 7 segment display, not an LCD screen.
- The surgeon will not touch the button it self, as the button is connected to the dispencer it self, and it wont be touched by the surgeon
- The aim of the study, is to see if a countdown timer will help the surgeons to scrub during the whole 2 min, we have a clock on the wall but it does not help.
- The rules in our department is scrubing during 2 min, it does not matter if it is the first surgey or the last one, scrub time is always 2 min.
- when programming the prototype in arduino i took in consideration that the switch is disabled once the timer is started, so it does not matter how many times the surgeon hits the switch. the only things that will reset the timer is the end of the 2 min.
You mean they don't want to?
It probably won't have an effect again, unless you make them do it somehow.

The 3x7 segment display is not good by my opinion. You have 8 LEDs on each display, if we count 5mA per LED = 24*5 = 120mA.
 

jpanhalt

Joined Jan 18, 2008
7,929
As pointed out (post #9), if you use a 3-digit, 7-segment LED display, power consumption by the MCU is probably insignificant by comparison.

As for the project itself, it appears the hypothesis is that surgeons aren't scrubbing for the prescribed time, because they can't read a wall clock or don't know what the time should be. ;) If the idea is to police each scrub sink for compliance, have the surgeons bought into that idea? And, if there is a violation, what will the penalty be?

In my experience, the best and maybe only way to effect change is to have them buy into the project and produce meaningful results. One thing they are sensitive to is individualized post-op infection rates. Do you plan to correlate compliance with your scrub protocol (particularity for surgeries after the first of the day) with post-op infection rates? Lacking something like that, the project risks being viewed as an inconvenience at best by the surgeons.
 

jpanhalt

Joined Jan 18, 2008
7,929
Along with an automatic pink slip.

A surgeon who does not follow the posted policies has no business being a surgeon. Negligence costs lives.
For most hospitals, surgeons carry a lot of weight. The bludgeon approach does not work. As one example, surgeon-specific infection rates are collected and known. So, why not publish them? There may be some hospitals that do that today, but over the years of my experience, I have never come across one that did. I have also never come across a surgeon who wouldn't respond to procedures that improved outcomes.

As for negligence, one would need to show a correlation between a 2-minute or any other arbitrary scrub time for second and subsequent surgeries and outcome. There might even be a few surprises. Operating room personnel are rightfully concerned about the adverse effects of frequent and excessive scrubbing.
 

danadak

Joined Mar 10, 2018
3,578
One approach, using PSOC. Notice most of chip resources (right hand window)
in this example unused. For example you could detect room brightness and
control a back light for the display with the analog and A/D capabilities also
inside chip. And PWMs inside for controlling back light.

The Seg LCD component (component is a resource inside chip) can be configured
for quite a few displays.

This example is being put into sleep mode and periodically woken up.

upload_2018-12-6_12-27-46.png

Regards, Dana.
 

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