Timeout (again)

friis

Senior Member
Hi AllyCat,
Thank you for your remarks. I have checked the power consumtion 08M2 and get the following:

pause M16 1.14 mA
K250 0.27 mA

sleep M16 0.07 mA
K250 0.07 mA

So it seems that the job is to reduce the power consumption of HC-12 and the H-bridge/valve.

I am trying a transistor switch for that - without much luck so far.
torben
 

inglewoodpete

Senior Member
Hi AllyCat,
Thank you for your remarks. I have checked the power consumtion 08M2 and get the following:

pause M16 1.14 mA
K250 0.27 mA

sleep M16 0.07 mA
K250 0.07 mA

So it seems that the job is to reduce the power consumption of HC-12 and the H-bridge/valve.

I am trying a transistor switch for that - without much luck so far.
torben
I'd suggest a high-side switch. The HC-12 needs up to 200mA, depending on transmit power level, but can work OK down to 3.2 volts. So a small signal NPN (Eg BC548 or equivalent) driving a slightly stronger PNP (Try a BC327 or equivalent) should do the trick.
HighSideSwitch.JPG
 

AllyCat

Senior Member
Hi,

Yes, those current drains look about right. The 70 uA during sleep is probably because some hardware functions on the chip are still active, for example the Watchdog timer and Brownout detector. There are other functions such as the FVR and Comparators, etc. which might be active, but it's not clear (to me) which are included in the datasheet specification, or enabled/disabled by the PICaxe OS firmware.,

If you want to switch the HC12 supply, then certainly a high side switch is highly recommended, but a simple NPN emitter follower might be sufficient if the PICaxe is being supplied by 4 volts or more. However, the HC12 does also have an "ultra low power" mode (but not at 9600 baud, or for a high data throughput) and a "Sleep" command, but NOT a "Wake Up" command. So to wake up the HC12 you need to activate its command pin (or whatever they call it) and observe the specified delay periods (40 ms, If I Recall Correctly).

Cheers, Alan.
 

friis

Senior Member
Hi inglewoodpete and AllyCat,

I am at the moment looking at activating a H-Bridge/valve and for that I need the high-side switch.
Can one say something about the values of R1, R2 and R3 when the load resistance is 5 kOhm? Actually one of the H-Bridges I might use shows OL for the resistance between the + and - terminals.
I think that I have cooked some transistors and would like to start with reasonable values.
torben
 

inglewoodpete

Senior Member
Hi inglewoodpete and AllyCat,

I am at the moment looking at activating a H-Bridge/valve and for that I need the high-side switch.
Can one say something about the values of R1, R2 and R3 when the load resistance is 5 kOhm? Actually one of the H-Bridges I might use shows OL for the resistance between the + and - terminals.
I think that I have cooked some transistors and would like to start with reasonable values.
torben
I would use a 1k to 4.7k resistor for R1. Try 4.7k for R2 - this can be reduced as low as 1k if Q2 does not turn on sufficiently. R3 is just to ensure that Q2 turns off fully, so I'd use 10k.
 
Top