Hi,
I seem to always struggle when it comes to thinking about how to power my Applications. It's easy prototyping each individual component with a bench power supply, but as soon as I need them all in one circuit everything gets harder for me. Any tuorials or reading matriel to master this dark art would be appricated.
I need help with this specific example:
I want to use this device :https://octopart.com/wise-4012e-ae-wa-advantech-67312669
Runs at 1.5w@5vdc and consumes 300mA.
I want to power this sensor separately but output attached to device above : **broken link removed**
Runs at 12 - 24vdc and consumes 30mA - 0.36watts
I require that these devices must run for over 5 days on a battery pack.
I have found this battery : https://www.powerstream.com/PST-MP3500-I.htm
it has a value of 60wH and is about £140
or this battery : https://www.ebay.co.uk/itm/External...attery-Charger-For-Mobile-Phone-/291613962290
It has a value of 50000maH and costs £11.49
SO! for the two battery packs about my calculations are:
for 60wH : 60wH/(1.5w+0.36w) = 60wH/1.86w = 32hours = 1 dat 3 hours
for 50000maH: 50000mAH/(330mA) = 151 hours = 6 days
Are my calculations above correct and why does the significantly cheaper option last longer?
One other thing to consider is that the ratings of batteries sold on ebay is VERY optimistic. I think these battery packs are made up of a number of 18650 lithium ion cells. As the dimensions given for the 50 AH unit is 165mm x 80mm x 22mm I think it will contain 8 of these cells. The rating of these units is given in the AH rating of the cells so by the time it is stepped up to 5 volts it will be less Batt AH * 3.3/5 * 0.9 (90% efficiency of step up converter) = 0.594 So even if the basic battery pack was 50 AH that would only be 29.7 AH. The largest capacity 18650 cells that I have seen advertised is 4.9 AH I bought some of these and none had a capacity of more than 2 AH If you Google "18650 cell capacity" you will find that many other people have also found this. I think the best genuine capacity is about 3.6 AH So if we use this figure with 8 cells we get 28.8 AH (This is at 3.3 volts) so when we correct for the output at 5 volts we get 28.2 * 0.594 = 17.1 AH (= 85.5 watt hours) I would think the one sold on ebay would probably have about half this rating.
Les.
(1) WISE-4012ZE: 5V @ 300mA= 1.5W
(2) E3Z-R86: 12V @ 30mA= 360mW
(3) TOTAL POWER= 2.16W
If the figure above is correct,
The sensor runs on 12 V, not 5 V, so the 5 V needs to be boosted to 12 V and that boosting will be only about 75% efficient. It will take about 0.5 W at 5 V to deliver 0.36 W at 12 V, so your total load at 5 V is closer to 2 W or 400 mA.
It is not. 1.5 + .36 = 1.86, not 2.16
Also, what is the reason for ignoring power losses due to power conversion efficiency once the OP says he wants to buy real world batteries and operate a real world device?
ak
Hi Spec.
I'm afraid its top secret, but I think you can deduce what I'm trying to do your self
But! Analogue Kid. About his calculation : 60 W-h at 5 V equals 12 A-h. 50000 mA-h at 5 V = 50 A-h = 250 W-h. 250 / 60 = 4.167. 50 / 12 = 4.167.
I'm not sure why you use the term efficiency? Efficiency in this case would be Power out / Power In?
Hi AK,Would the temperature effects reduce the available power by 25%?
ak
Thanks for that Spec
But i have to make this design as un-obtrusive as possible, A battery like the one above will not go down well in a factory( I suppose i should of told you that)
LiIon are usally compact and take up less room, the lead acid option above looks like it has the right specs but it is too big, are there any smaller options?
Please bare in mind guys that the PST-M3500 Has a 5v volt USB output for the Wise unit and also another DC output which can be set to a voltage between 5v and 19v and supply up to 4 Amps, so no extra circuitry needed?
The end design needs to be able to Run the WISE unit, an Opto Reflective sensor for counting items and also maybe up to 3 light intensity sensors.
I am currently liaising with SICK sensors to find the right type, low power etc. also for the WISE units Digital inputs i need the sensor to have a dry contact ? i.e. short D0 to GND. Please would somone be able to confirm that.
In the spec it says Dry Contact 0pen 1:close to GND. But i've measured the voltage between D0 and GND and there is a 5 volt potential. So i think the Sensor needs to be the dry contact ?
Robo
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?