MIller Solar Engine 1381 replacement?

[kaczchris]

After comparing the data sheet waveforms between the 1381 and the DS1817 I now see what your problem is. As is (no additional circuitry) the DS1817 will not replace the 1381. There is nothing in your circuit to turn it off after it's triggered.

Chris

well that would explain the behavior that it just trips open and never closes...


why does the 1381 snap back when the lower voltage is reached but the DS1817 does not?

(please excuse me if this is a "stupid" question. When it comes to electronics I am self taught with the help of books and the internet. I find that I have huge holes in my knowledge all the time.)

 

[(*steve*)]

OK, I'm looking at the datasheets

The 1381 is here. The DS1817 is here.

There is a significant difference between the two of these.

The 1381 (see page 7) turns ON a short time after the power reaches the upper limit of the voltage range, and stays on until the voltage falls below the lower limit of the voltage range. This chip provides a "power good" signal that (in one case) will turn on at 3.3V and turn off again at 3.0 volts.

The DS1817, on the other hand, provides a reset signal. This is triggered once as the voltage rises to the trigger point (for some fixed period) and then again as the voltage falls. The intent is to trigger a reset when power becomes good, and hold a reset as power fails.

Both perform a totally different function.

What you're probably looking for is a "power good" detector in a TO-92 package.

However, if you search digikey for the MN1381, you'll find they have three types in stock. They have trigger voltages ranging from 2.4 to 3.8 volts.

 

[(*steve*)]

Another option is the A-808xxCLY which is similar in operation to the 1381 other than it has a smaller hysteresis (it's 5% rather than 0.3 volts).

The S805 series is similar.

 

[CDRIVE]

Steve, at present we have two topics involving the Solar Engine. The other one is using the MN1381 but has issues when driving a heavier load. After comparing both Data Sheets I've concluded that both of them have some parameters that were extremely confusing until I read them repeatedly. Either that or it's the way they wrote that parameter or result.

They do seem to have one thing in common though, neither should be considered a current workhorse. The 2N3904, that both topics are using as drivers, isn't the biggest Beta bat on the ball field.

Chris

 

[kaczchris]

Thank you both for your responses.
It has been very helpful and educational!

 

[(*steve*)]

I think I might consider switching a small logic level mosfet. Most are going to give a relatively good Ids even at a relatively small Vgs, and the lack of current drive is less likely to be an issue.

However, it might also be reasonable to look at a darlington pair for the switching.

The voltage detectors with inverted outputs might be suited to driving a P channel mosfet as a high side switch. The open drain output would be ideal. A relatively high value resistor between gate and source would turn the mosfet off and not contribute to any static current drain.

 

[CDRIVE]

Steve, I thought so too but neither thread specified the motor current. The manufacturers spec Vgs(Thld) at an extremely low Ids.

Chris