Open jlamperez opened 8 years ago
Excel with the links for the necessary components to use LM2576 switched regulator:
Thanks @jlamperez. I'm ok purchasing those parts but the xlsx provided has broken links and they point at digikey.com (instead of digikey.es).
Can you provide the links again (a simple list here would do) in the .es domain?
Sorry, here you have in .es domain. The quantity column matches with the number of components to buy to build one prototype.
Quantity | Vendor P/N | Item Description | Link |
---|---|---|---|
1 | 553-1562-5-ND | FIXED IND 150UH, 2A, 100 MOHM TH, THROUGH HOLE | http://www.digikey.es/product-search/en?keywords=PE-53113NL |
1 | 493-1495-ND | CAP ALUM 680UF, 20%, 10V, RADIAL THROUGH HOLE | http://www.digikey.es/product-detail/en/nichicon/UHE1A681MPD6/493-1495-ND/589236 |
1 | 565-4405-ND | CAP ALUM 100UF 20% 25V THROUGH HOLE | http://www.digikey.es/product-detail/en/united-chemi-con/EFL-250ELL101MH07D/565-4405-ND/5824608 |
1 | LM2576T-5.0/NOPB-ND | IC REG BUCK 5V 3A TO220-5 | http://www.digikey.es/product-detail/en/texas-instruments/LM2576T-5.0%2FNOPB/LM2576T-5.0%2FNOPB-ND/212636 |
1 | 1N5820DICT-ND | DIODE SCHOTTKY 20V 3A DO201AD | http://www.digikey.es/product-detail/en/diodes-incorporated/1N5820-T/1N5820DICT-ND/190969 |
2 | 2N7008-G-ND | MOSFET N-CH 60V 0.23A TO92-3 | http://www.digikey.es/product-search/en?keywords=%092N7008-G-ND |
ordered.
2016-04-25 12:28 GMT+02:00 Jorge notifications@github.com:
Sorry, here you have in .es domain. The quantity column matches with the number of components to buy to build one prototype. Quantity Vendor P/N Item Description Link 1 553-1562-5-ND FIXED IND 150UH, 2A, 100 MOHM TH, THROUGH HOLE http://www.digikey.es/product-search/en?keywords=PE-53113NL 1 493-1495-ND CAP ALUM 680UF, 20%, 10V, RADIAL THROUGH HOLE http://www.digikey.es/product-detail/en/nichicon/UHE1A681MPD6/493-1495-ND/589236 1 565-4405-ND CAP ALUM 100UF 20% 25V THROUGH HOLE http://www.digikey.es/product-detail/en/united-chemi-con/EFL-250ELL101MH07D/565-4405-ND/5824608 1 LM2576T-5.0/NOPB-ND IC REG BUCK 5V 3A TO220-5 http://www.digikey.es/product-detail/en/texas-instruments/LM2576T-5.0%2FNOPB/LM2576T-5.0%2FNOPB-ND/212636 1 1N5820DICT-ND DIODE SCHOTTKY 20V 3A DO201AD http://www.digikey.es/product-detail/en/diodes-incorporated/1N5820-T/1N5820DICT-ND/190969 2 2N7008-G-ND MOSFET N-CH 60V 0.23A TO92-3 http://www.digikey.es/product-search/en?keywords=%092N7008-G-ND
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@jlamperez, parts arrived. I'm taking a flight tomorrow and coming back next Thrusday. If you'd like the parts before Thrusday, reach out @imuguruza.
Can I go today to take them? Also I have some questions about the PCB I have designed it will be a problem?
That's fine. Can you come before 5PM?
2016-04-29 15:05 GMT+02:00 Jorge notifications@github.com:
Can I go today to take them? Also I have some questions about the PCB I have designed it will be a problem?
— You are receiving this because you commented. Reply to this email directly or view it on GitHub https://github.com/erlerobot/smart_motor/issues/36#issuecomment-215705839
Yes, but I need one hour more or less.
No problem.
2016-04-29 15:07 GMT+02:00 Jorge notifications@github.com:
Yes, but I need one hour more or less.
— You are receiving this because you commented. Reply to this email directly or view it on GitHub https://github.com/erlerobot/smart_motor/issues/36#issuecomment-215706250
New voltage regulator
Since the voltage regulator we have now only gives 300 mA maximum current to the output load, this week I was searching for a new one with an output current between 1 and 1.5 A, in order to power the raspberry pi, the ADC and the temperature sensor.
The raspberry pi more less needs 600 mA to operate correctly and then 100 mA more for each USB. The raspberry pi one only has one mini USB but because we are working also with the one and two and using three USB connections for mouse, keyboard and Wifi I will do the operations for the worst case.
Maximum current needed in the worst case: Imax = 600 mA + 3x100 mA + 300mA(old regulator) = 1.2 A.
So based on this calculation I started the search.
LDO regulators
Calculations: Power dissipation: Pdmax = (Vi - Vo) x Io , Iq of the linear regulator is ignores due to its relative small size to Io. Device's thermal resistance from junction to ambient: Θja max = (Tj – Ta)/Pdmax
So for and ambient temperature of ->Ta = [25 and 35], junction temperature in datasheet of 0-125ºC -> Tj = 125-15 = 110ºC.
LM340-N/LM78XX: Pdmax = (12 - 5) x 1 = 7W and Θja max = (110 - 35)/7 = 10.7 ºC/W. If we compare this values with the thermal resistance from junction to ambient for different package:
µA78xx: Pdmax = (12 - 5) x 1.5 = 10.5W and Θja max = (110 - 35)/10.5 = 7.14 ºC/W.
Therefore in all cases we can see that the Θjamax is lower to the Θja for every package, this means that we will need a heatsink for our PCB or move to a switching power solution. I will choose the second one.
Switching power solution
I use Buck topology regulator: This ones reduce DC voltage to a lower DC voltage. This kind of regulators not need heatsink like LDO regulators.
There are tow different options here, one would be to embedded a module directly to the PCD, and the other is to find a IC and calculate the surrounding components needed for this Buck regulator or Step-Down Voltage Regulator.
Here I have done the calculations for the LM2576.![captura de pantalla de 2016-04-23 13 08 40](https://cloud.githubusercontent.com/assets/8319840/14761039/a7970846-0954-11e6-85e7-97e09d4428a2.png)
We will need the next components besides the LM2576:
For our application Vout = 5V, Vin(max)= 12V, I load(max) = 1.5A.
Calculations
Total power dissipated by the LM2576 can be estimated as follows: PD = (VIN)(IQ) + (VO/VIN)(ILOAD)(VSAT) = 12 x 10mA + (5/12) x 1.5 x 2 = 1.37W.
When no heat sink is used, the junction temperature rise can be determined by the following: ΔTJ = (PD) (θJA) = 1.37 x 45 = 61.65.
To arrive at the actual operating junction temperature, add the junction temperature rise to the maximum ambient temperature. TJ = ΔTJ + TA = 61.65 + 35 = 96.95 < 110ºC.
So this calculations validate that it is not needed a heatsink now.