Sorry about my last. I was working from your original post, then I had a system crash and when I returned I was looking at the last line of your recent post, which actually does have much more information. A doofus moment on my part.
I still have the question “what is your requirement for run time”? If it’s more than several hours, you’ll need a bigger battery, or else go into sleep mode or some other reduced current mode when possible.
From: Joe Rocci
Sent: Wednesday, January 10, 2018 7:19 AM
To: [gcbasic:discussion]
Subject: Re: [gcbasic:discussion] RE: [gcbasic:discussion] Coin powered projects
George
In order to get a precise answer, we’ll need precise information:
1) Describe the application and special functional requirements.
2) What is the hardware platform (commercial board, home brew PIC, etc)?
3) How long is the battery expected to run? Will it run continuously or does the device “sleep” when not in use?
4) How often do you expect to replace or recharge the batteries?
5) Are there size/weight/cost constraints?
6) What is the current draw of each piece of the system? If you don’t have specifications, get a $5 meter and measure it.
7) Is it imperative to use coin cells?
Your final question points out the difficulty in getting good advice: “...has anybody been able to find a good match that does work well?”. Please define your requirements more precisely. As an engineer to an accountant I think we’ll both agree that specificity in communications is essential to getting a good result.
From: George Alvarez
Sent: Wednesday, January 10, 2018 12:03 AM
To: [gcbasic:discussion]
Subject: [gcbasic:discussion] RE: [gcbasic:discussion] Coin powered projects
Hi, thanks. Before I begin, please understand that I know next to nothing about this stuff. They don't teach you any of this in accounting school.
I've checked with the seller I bought the LCD from, and he hasn't gotten back to me, but there is a similar one that draws 0.04W. If I can use the internet correctly, 0.04 W @ 3.3V = 12 milliamps operating current for the LCD.
The button doesn't really draw current, other than whatever the pin might put out when the circuit closes, I guess. It's a momentary switch, so we're probably more concerned about spikes, when it is pushed. I'm putting 5V in, and using a 10K pull up resistor.
I can't find the right info for the Arduino nano. But for the ATMega328p, I found this:
The literature says that each I/O pin is rated at 40mA. That sounds like a maximum. There are several values provided for pin 27, leakage a 1uA, and worst case, 5.5mA when active. The uA are negligible, so let's use 6mA when the thing is running and a button is being pushed.
Without whatever else the arduino nano is using, that's 18mA consumption when it is used. A typical coin cell battery in the size range I'm using has about 35mA capacity. So two hours on a good day?
The trouble is that I can't run my project for even two seconds on a coin cell. I have connected two cells in series, to double the voltage to roughly 5.7V, and the only thing that happens is that I get a repetitive blink on an on-board LED, which acts exactly likes the most basic of programs that comes with that board. I've tried with and without a voltage regulator, but it simply doesn't work.
I got the bright idea to switch to two AA batteries and put them through the voltage regulator, and I figured I could time how long they stayed alive, and do the math from there to arrive at current consumption. But my voltage regulator doesn't work at < 2.8 input volts, and sure enough, the battery drain at about 24 hours of constant use drained the voltage down to 2.8 and my project died overnight.
According to this link a Duracell battery under a 0.2A load will drop from 1.5 volts to 1.2 volts after about an hour. Assuming consumption is roughly linear, then 0.02A should do the same thing in maybe 10 hours. From the time I started to the time I checked in the AM, that's in the right ballpark.
So, my conclusion is that my arduino board and coin cells are not a good match. I'd love to hear your thoughts on what I just reported, and what I may have left out. Again, I know next to nothing about all this, and many times, my assumptions are completely wrong. You will not offend me with corrections.
But assuming I'm pointing in the right direction, the question is, has anybody been able to find a good match that does work well?
George
Sorry about my last. I was working from your original post, then I had a system crash and when I returned I was looking at the last line of your recent post, which actually does have much more information. A doofus moment on my part.
I still have the question “what is your requirement for run time”? If it’s more than several hours, you’ll need a bigger battery, or else go into sleep mode or some other reduced current mode when possible.
From: Joe Rocci
Sent: Wednesday, January 10, 2018 7:19 AM
To: [gcbasic:discussion]
Subject: Re: [gcbasic:discussion] RE: [gcbasic:discussion] Coin powered projects
George
In order to get a precise answer, we’ll need precise information:
1) Describe the application and special functional requirements.
2) What is the hardware platform (commercial board, home brew PIC, etc)?
3) How long is the battery expected to run? Will it run continuously or does the device “sleep” when not in use?
4) How often do you expect to replace or recharge the batteries?
5) Are there size/weight/cost constraints?
6) What is the current draw of each piece of the system? If you don’t have specifications, get a $5 meter and measure it.
7) Is it imperative to use coin cells?
Your final question points out the difficulty in getting good advice: “...has anybody been able to find a good match that does work well?”. Please define your requirements more precisely. As an engineer to an accountant I think we’ll both agree that specificity in communications is essential to getting a good result.
From: George Alvarez
Sent: Wednesday, January 10, 2018 12:03 AM
To: [gcbasic:discussion]
Subject: [gcbasic:discussion] RE: [gcbasic:discussion] Coin powered projects
Hi, thanks. Before I begin, please understand that I know next to nothing about this stuff. They don't teach you any of this in accounting school.
I've checked with the seller I bought the LCD from, and he hasn't gotten back to me, but there is a similar one that draws 0.04W. If I can use the internet correctly, 0.04 W @ 3.3V = 12 milliamps operating current for the LCD.
The button doesn't really draw current, other than whatever the pin might put out when the circuit closes, I guess. It's a momentary switch, so we're probably more concerned about spikes, when it is pushed. I'm putting 5V in, and using a 10K pull up resistor.
I can't find the right info for the Arduino nano. But for the ATMega328p, I found this:
The literature says that each I/O pin is rated at 40mA. That sounds like a maximum. There are several values provided for pin 27, leakage a 1uA, and worst case, 5.5mA when active. The uA are negligible, so let's use 6mA when the thing is running and a button is being pushed.
Without whatever else the arduino nano is using, that's 18mA consumption when it is used. A typical coin cell battery in the size range I'm using has about 35mA capacity. So two hours on a good day?
The trouble is that I can't run my project for even two seconds on a coin cell. I have connected two cells in series, to double the voltage to roughly 5.7V, and the only thing that happens is that I get a repetitive blink on an on-board LED, which acts exactly likes the most basic of programs that comes with that board. I've tried with and without a voltage regulator, but it simply doesn't work.
I got the bright idea to switch to two AA batteries and put them through the voltage regulator, and I figured I could time how long they stayed alive, and do the math from there to arrive at current consumption. But my voltage regulator doesn't work at < 2.8 input volts, and sure enough, the battery drain at about 24 hours of constant use drained the voltage down to 2.8 and my project died overnight.
According to this link a Duracell battery under a 0.2A load will drop from 1.5 volts to 1.2 volts after about an hour. Assuming consumption is roughly linear, then 0.02A should do the same thing in maybe 10 hours. From the time I started to the time I checked in the AM, that's in the right ballpark.
So, my conclusion is that my arduino board and coin cells are not a good match. I'd love to hear your thoughts on what I just reported, and what I may have left out. Again, I know next to nothing about all this, and many times, my assumptions are completely wrong. You will not offend me with corrections.
But assuming I'm pointing in the right direction, the question is, has anybody been able to find a good match that does work well?
Thanks again.
RE: [gcbasic:discussion] Coin powered projects
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