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I am building a kicker for a soccer robot and need help understanding the electrical diagram.

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Mblizzard

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I am attempting to build the electrical circuit in the diagram that i have attached, it is a kicker for a soccer robot. I have ordered the chipset online an I got everything else at Jaycar except the solenoid. I don't know which solenoid to get (watts, current etc.) and i don't know how to find out, can anyone please help?

PS. This is a robotics project, not homework, if i have posted it in the wrong section please let me know.
 

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Pommie

Well-Known Member
Most Helpful Member
The solenoid can be whatever the power transistor and power supply can handle. However, there is a problem with that circuit, it will powerup with the solenoid activated. So, it will give an uncommanded kick when you turn it on. To fix this requires changing the transistors to pnp type. Do you know how to do this?

Some random questions.
How big is the robot?
Is it for a competition?
Is there an example we can see?

Mike.
 

Mblizzard

New Member
The solenoid can be whatever the power transistor and power supply can handle. However, there is a problem with that circuit, it will powerup with the solenoid activated. So, it will give an uncommanded kick when you turn it on. To fix this requires changing the transistors to pnp type. Do you know how to do this?

Some random questions.
How big is the robot?
Is it for a competition?
Is there an example we can see?

Mike.
No, i don't know about pnp transistors, The robot is circular with a 210mm diameter, it is for the RCJA Lightweight soccer competition and for examples just google RCJA Lightweight/Open soccer and go to images.

This runs a kicker off an EV3 Sensor Port, so, are you saying that the firs time that i turn the bot on it will kick? If so that does not matter provided that there is no delay... but with the need to charge the capacitors I'm not sure how that could happen...
 

Les Jones

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Most Helpful Member
The capacitors will be charged via the 1 K resistor. The total stored energy in the capacitors wil be discharged into the solenoid. Yo could modify the circuit to store more energy by increasing the value of the capacitors or using higher voltage capacitors and charging them to a higher voltage. The stored energy is proportional to the suuare of the voltage.

Les.
 

Grossel

Well-Known Member
I don't know the nature of PCF8574 and can't speak for that part. But - do you realize that you loose about 0.7V due to voltage drop over Q2 when used in a set of darlington transistors? So you won't get 4.3V but rather 3.6V over the solenoid coil.

Do you know how much current that the solenoid need? I suspect that you would actually be better off without Q1, after all the emitter resistor is quite low as it is.
 

Pommie

Well-Known Member
Most Helpful Member
Sorry, missed the bit where it's powered by capacitors that won't be charged.

Just looking at the rules of the kicker power, it would make sense to make the kicker adjustable. This can be done by adjusting the charging voltage of the capacitors. Something like this would allow you to tune the kicker using a voltage between 5 and 35 volts. To use this module remove the 1K resistor that charges the caps and use the module to charge them via a suitable current limit resistor (100Ω should do).

Mike.
Edit, thinking about this, using the above chip is not a good idea. It would be much simpler to drive a mosfet direct from a micro output. This way you have control over the on time. A solenoid rated at 20W can be powered at 100 - 200W as long as the time is short. I would imagine a kicker does it's work in less than a fiftieth of a second. Might be worth some experimenting.
Edit2, where about are you based?
 
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