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Did you watch the video? It explains this. 1.95KHz works well the R1 C1 filter that converts the PWM signal to DC. 490 Hz might work, or you might have to change the values of R1 and C1 to get a clean DC signal. Just try it with 490 Hz and check if you have a good clean DC signal on the base of the transistor. It will probably work fine.

The existing R2, C1, R 1 values should work as they are just a filter for the PWM signal from the Arduino and also to make sure the MOSFET turns off when it should. You should be able to put 20 volts across the mosfet but make sure that you only apply a low. Voltage to the Arduino, I.e use the USB cable from your computer to power the Arduino or an approximate 5 volt supply.

The circuit is correct. The 10k pulls up the reset pin and disables it. The microcontroller is reset by a momentary negative pulse which comes through the capacitor from the programming jack.

No I did not think of doing that but it sounds like it could work.Simon

Hi Ron,Yes it would be possible but you would have to make major changes to the program and electric circuit. It would essentially be a brand new project, very different from the existing one. I'm not familiar with this display, I've never used it and I don't have one or time to try this modification at present. If I ever do in the future I'll let you know.

Hi Randy,yes you can. If they are common anode type, just connect the anode of each display to the transistor emitters, that will control which display is active at any one time. Connect all of the display A pins together, all of the B pins together etc. You can also use common cathode type displays if you remove U2 from the circuit and connect the resistors on its output directly to U7, then connect the transistor collectors to the display Gnd pin and transistor emitter to circuit ground. This will work I think.Good luck,Simon

Don’t know for sure, but I’d guess you’d need to double the values of R1, R3 and R4. Try that and see if it works. In this case R3 will need to be 1/2 watt absolute minimum, probably better to use 1 watt.

The MAC97A4 is a sensitive gate type triac.The data sheet for the BT131-600 say is a very sensitive gate, so it will likely work also. As long as its voltage and current carrying capabilities are what you need for your application you should be okay. This stuff is cheap, buy one and try it :-)

It should work. I’m not sure if a zener would be any faster. For this circuit you’d need to manually reset it though. With a zener the diode will just conduct during the overvoltage condition and stop by itself once the condition is cleared. Both should work and both should be very very fast. With a zener you’d need an appropriate series resistor or else your zener will burn out pretty quickly if power is applied for any length of time. With the circuit there’s no chance of burn out because it essentially turns of Q1 and removes power to the load.

Somewhere in the spec you’ll find there’s a minimum current required for the triac. Also need R1 to keep Q1 gate high and supply current to Led 2 during normal operation.You are partly correct about C1, you could get away without it. This just there to stabilize the circuit against very momentary over voltage spikes. So if you went over voltage for say 1 nanosecond only, you would not want the circuit to trip. C1 should slow down and prevent the trip response of Q1 in these cases.Try build it and play around with it. This circuit is somewhat experimental and you can probably vary the resistor and capacitor values somewhat depending on your application. For example if you wanted to use a higher voltage range, you’d need to change the value of R1 but I haven’t tried it.keep building and exp…

Somewhere in the spec you’ll find there’s a minimum current required for the triac. Also need R1 to keep Q1 gate high and supply current to Led 2 during normal operation.You are partly correct about C1, you could get away without it. This just there to stabilize the circuit against very momentary over voltage spikes. So if you went over voltage for say 1 nanosecond only, you would not want the circuit to trip. C1 should slow down and prevent the trip response of Q1 in these cases.Try build it and play around with it. This circuit is somewhat experimental and you can probably vary the resistor and capacitor values somewhat depending on your application. For example if you wanted to use a higher voltage range, you’d need to change the value of R1 but I haven’t tried it.keep building and experimenting!cheers,Simon

Hi Jacobtohahn,Thanks for your question.R1 is there to provide enough current for Q2 to turn on when triggered. If LED 1 is not conducting then R3 cannot supply this current.R2 is there to turn off Q1 by pulling its gate to ground when power is removed from the gate. Look up MOSFET theory when you have time. Once Q1 has been turned on, the gate needs to pulled firmly to ground to make sure it turns off.The purpose of C2 is to prevent high frequency noise on the power rails. Typically in digital circuits we place these near the power rails on each IC. In this case the only IC that could possibly generating noise is the Arduino IC. It will have decoupling caps on the Uno board anyway, but as a matter of good design you should include a decoupling capacitor across the power rail. Location wi…

Hi Jacobtohahn,Thanks for your question.R1 is there to provide enough current for Q2 to turn on when triggered. If LED 1 is not conducting then R3 cannot supply this current.R2 is there to turn off Q1 by pulling its gate to ground when power is removed from the gate. Look up MOSFET theory when you have time. Once Q1 has been turned on, the gate needs to pulled firmly to ground to make sure it turns off.The purpose of C2 is to prevent high frequency noise on the power rails. Typically in digital circuits we place these near the power rails on each IC. In this case the only IC that could possibly generating noise is the Arduino IC. It will have decoupling caps on the Uno board anyway, but as a matter of good design you should include a decoupling capacitor across the power rail. Location will be very specific to the particular circuit of course.Regards,Simon

Thank you tinman!

Hi Emin,glad to hear it is helping, all the best with your project. That crazy ISD1760 blew up so many micro controllers before I finally figured it out!best regards,Simon Carter

Can someone kindly describe to me in words and at a high level the methodology used here because I find the Arduino code very hard to follow because there are so few comments.So what I mean by this is does he shift in the first bit of the first row of the first word and then clock through all the rows etc. I.e how are the columns and rows clocked such that persistence of vision works? Or is there some similar code that I can look at that is well commented?Thanks you

The first one I built has been running for years with no leaks. The pressure is really low with this little pump. So I'd say the probability of a leak is low. The electric motor on the other hand needs to be protected from the weather. It would not last long outside of the protection of the enclosure.

Thanks Dave. Wow that's quite a list! I I'll look at incorporating these if I do another improved one. I especially like the idea of a dry reservoir alert and soil moisture measurement.Simon

I agree. I'm thinking about developing it further and making it solar powered. If I do that, then I'll probably do a proper PCI.

Yeah thanks for the encouragement. The parts are so small I can't even see them very well without a magnifying glass! Anyway I'll play around with it some rainy day...

Hi Vadim, Congratulations on an excellent project, thanks for posting. Would you or anyone else that understands it be able to post the Arduino code with full explanatory comments? Or an explanation of how the code works? For the Arduino beginner the program is very hard to understand. I would like to build something like this but without understanding the program, there is not a lot of point, because like anyone my objective is to completely understand how it works.Thank you for any help.Regardssimon

look on www.newegg.com on sale right now for $39

Thanks, appreciated