ATTINY2313 micro running aeroponic pump. Cycle time 30 sec. Duty cycle 50%.
JT D, [17.12.20 18:29]
On the left is a pc psu that powers the board and pump. Pump controlled with relay. Wouldn’t a MOSFET be preferable?
JT D, [17.12.20 18:30]
Timer is interrupt driven.
@Kush_agra_wal, [17.12.20 18:38]
Relay would give perfect isolation between controller and pump hence i guess in this case relay will be a better option and also the selection would depend on how much current is to be switched that depends on pump and i think relay can switch or control more current than MOSFET?
Kushagra Agrawal, [17.12.20 18:39]
Not sure of it👆
JT D, [17.12.20 18:53]
[In reply to Kushagra Agrawal]
True that isolation is excellent. The relay’s inherent isolation is 3.5kv. But PCB layout is very important to achieve that.
JT D, [17.12.20 18:54]
Current draw is 8A. Voltage is 12v.
JT D, [17.12.20 18:56]
There is a rs485 driver so that i can connect to a server like Raspberry PI. Should i use rs232 instead?
Kushagra Agrawal, [17.12.20 19:15]
[In reply to JT D]
But then to draw this max amount of current we would need a high gate voltage to control the switching so it may be possible that micro controller been used won’t supply this through its I/O port? Means again it would need configuration, if possible, to be used?
Kushagra Agrawal, [17.12.20 19:17]
And in this aeroponic farm the data is collected from multiple points or a single point?
JT D, [17.12.20 20:22]
[In reply to Kushagra Agrawal]
Multiple.
JT D, [17.12.20 20:32]
[In reply to Kushagra Agrawal]
To drive the relay we use a transistor. The relay requires 12v. The transistor is TIP122 connected to 12 v. So a gate drive of 12 v is quite feasible. We will save space and have a far longer life for a transistor, but it probably wont save us any money.
design optimisation- cost, space, reliability, manufactureability, serviceability…
If we were making several thousand, it would definitely be a MOSFET.
Kushagra Agrawal, [17.12.20 20:42]
[In reply to JT D]
Then rs485…cause i think with rs232 you can connect only one device. Like rs232 was used with db9 cable for printer and computer connection.
Kushagra Agrawal, [17.12.20 20:45]
And selection would also depend on basis which proto is faster among rs485 and rs232 as data would be transferring.
JT D, [17.12.20 21:01]
[In reply to Kushagra Agrawal]
Yes. RS485 is a balanced line multi drop system.
Speed will be slower than a RS232 as it is half duplex - unless we separate the tx and rx lines. However the amount of data is very sparse. So a very low speed would be perfectly ok.
@Anool jokingly suggested a 555 timer
Anool Mahidharia, [17.12.20 18:54]
[In reply to JT D]
Looking good.
Although, a 555 would have done the job !!
JT D, [17.12.20 19:04]
[In reply to Anool Mahidharia]
. Yes. Unfortunately water level and rs485 link are likely to mess up a 555, though we could implement a 556 level control.
Anool Mahidharia, [17.12.20 19:05]
LOL, just kidding. gotta get in a 55 joke at every opportunity.
JT D, [17.12.20 19:10]
[In reply to Anool Mahidharia]
. But seriously a fully discrete transistor implementation would be fun.
JT D, [17.12.20 19:11]
After all blokes are building cpus with transistors