I have been working on the attached block diagram, I can't figure out why relay isn't working and pnp sk100 transistor can have alternative in proteus as?
I'm attaching the details of components to be used. I'm making this using hex inverter and ne555 timer components. if possible can you provide me it's circuitry on proteus? .
Values of the Components in the Circuit:

• Capacitor (C4) = 10u 16V.
• Capacitor (C5) = 0.01u.
• Resistor (R3) = 27K
• Resistor (R4) = 27K
• Diode (D1 and D2) = IN4148
• Relay = 6V, 150 ohms

Regards
Shikhil Sharma

 

Welcome to AAC!
Sorry, can't help with Proteus, but I have a few comments on the circuit.
1) For soil moisture sensing, the probes will corrode due to electrolysis if energised with DC. Better to use AC to slow the corrosion.
2) What is the purpose of D1/R2? They are shorted out.
3) Your relay is 6V rated but the supply voltage is 9V.
4) The standby current of standard 555 timers is significant and will drain a little 9V battery faster than the CMOS versions.
5) 555 timers (even the CMOS versions) are not good for consistent time delays more than a few tens of seconds. What delays are you designing for?
6) With no hysteresis there is likely to be jitter at the 7404 output.

 

appreciate your response,
1. yah! probes will corrode but it's for least time use.
2. they are shorted out, I don't know why but I'll let you know.
3. The supply voltage is 9v 'cause it has to also drive NE555 and if you have any other suggestion, most welcome.
4. battery should be __?__Volts.
5.delays may be of few hours.
6. what to do for hysteresis?

 

Welcome to AAC!
Sorry, can't help with Proteus, but I have a few comments on the circuit.
1) For soil moisture sensing, the probes will corrode due to electrolysis if energised with DC. Better to use AC to slow the corrosion.
2) What is the purpose of D1/R2? They are shorted out.
3) Your relay is 6V rated but the supply voltage is 9V.
4) The standby current of standard 555 timers is significant and will drain a little 9V battery faster than the CMOS versions.
5) 555 timers (even the CMOS versions) are not good for consistent time delays more than a few tens of seconds. What delays are you designing for?
6) With no hysteresis there is likely to be jitter at the 7404 output.

VERY good point on #1.....the same issue exists when doing volume ground conductivity measurement for R.F. design work! I learned this the hard way. LOL

 

what can replace pnp sk100? or what is alternative for pnp sk100 transistor?

 

1. U3A (7404) has no negative rail power connection. Also, it cannot run on 9 V.

2. You say the circuit is not working, but you don't say what is wrong or what "working" is. What is the circuit supposed to do. When should the relay activate, for how long, and why?

3. It looks like the intent is an oscillator that is gated by a monostable that is triggered by something. If so, U1's output cannot connect directly to U2's timing network. U2 will not oscillate under any conditions.

4. If the intent of the 7404 is to act as an input conditioner that generates a fast edge when the input conditions requires it, change the 7404 to a CD40106 or CD4093. These have Schmitt trigger (hysteretic) inputs stages and can run on 9 V.

5. Also, if #4 is correct, then everything can be done with one CD40106, eliminating both 555's

6. Change the relay to one rated for 9 V operation. Alternative - change to a 12 V relay (easier to find) and a 12 V battery.

7. U2 oscillates at 1.8 Hz. Each time the relay is activated, it is on for less than 1/2 second. Is this really your intent?



ak

 

Almost any PNP transistor (e.g. a 2N3906) will do for Q1 (which, incidentally, should have a current-limiting base resistor), unless your relay is particularly current-hungry.

 

what can replace pnp sk100? or what is alternative for pnp sk100 transistor?

If the relay coil current is less than 100 mA, U2 can drive it directly without the transistor.

ak

 

5.delays may be of few hours.

Very long R-C timers are wildly inaccurate and drift with time and temperature. Better to use a higher-frequency oscillator and a divider to get to the times you need. Depending on the on time / off time ratio, the decoding can be very simple.

ak

 

If the 9V battery looks like square cookie then using relay will draw too much current, and it can't working too long, what you trying to connect with the contacts of relay?

Or maybe you can using mosfet to replace relay.

The input of second 555 quite strange.

The pin 7 of 7404 should be connected to Gnd, then 7404 and 555 have a common ground.

 

Almost any PNP transistor (e.g. a 2N3906) will do for Q1 (which, incidentally, should have a current-limiting base resistor), unless your relay is particularly current-hungry.

Emitter follower - no base resistor required. Also, note the logic polarities. The 555 goes high to turn *off* the relay and activate the valve connected to the NC contacts.

Here is the original article. It does not have any timing information. In particular, it does not explain why it is activating the relay almost twice per second.

http://www.electronicshub.org/automatic-plant-irrigation-system/

Now, where did I leave my 820K pot...?

ak

 

Emitter follower - no base resistor required.

Good point. My bad.

 

This circuit is a mess. It has four major sections; two will not work and one is weird. Rather than try to fix it, what about another approach...

The circuit attempts to make a closed-lop watering system. When soil moisture gets below a certain level, the system adds water until it is above another level, then shuts off and waits to repeat. Both the time between waterings and the time the water is on can vary. Another approach is to have fixed time periods for both the watering time and the time between waterings. With this system, the only thing the sensor does is allow a watering cycle to happen. For example, if the system is set up to apply water for 2 minutes every hour, then at the top of each hour the sensor either allows the water to be applied (for a max of 2 minutes) or that cycle is skipped and the water remains off for the entire hour, when the soil is tested again. One CMOS counter, one NOR gate package, and an output transistor.

ak