Hello everyone - and a few questions!

[etmilosk]

Hello everyone,

my name is Milos, I come from Bosnia. I am an air traffic controller with a solid knowledge in hardware programming and electronics, and I am trying to build my first Ardumower.

First I would like to thank to all of you who made this great project possible, awesome work!

The biggest problem I find is trying to translate German documents and understand everything correctly.

Let me briefly explain my future Ardumower setup (I will open a separate thread later with all the details):

- The mower will be built from cheaper parts (mostly from China) because I need to keep the cost down.
- The wheel motors are Faurecia worm gear motors from eBay (12V, 17 rpm on output shaft, very powerful, ample amount of torque): link
- The mower motor is Chinese Gindun ZY6812 (24V, 3200 rpm, 80W): link
- The motor drivers are LN298
- The battery is 2 x Lead Acid 7 Ah battery, connected in series (for 24V): link
- The charger will be placed in the charging station together with the perimeter sender. The charger consists of a 30V 3.2A DC power supply which is digitally regulated to 29V 2A for optimal charging. The charging electricity will be transferred to the Ardumower via sliding contacts in the charging station.


I have several questions about the PCB assembly, and I would be grateful if someone could answer them to help me:

1. Can someone explain internal vs external charging? As far as I understand it, external charging is the case when a "smart" external charger is used (a charger which has charging control and balancing built in it), and internal charging is when a "dumb/stupid/simple" charger is used and in that case the PCB does the charging control via relay?

Is this correct? Is the charging that I will use called internal charging?

2. With this battery/charging setup, do I need both INA169 boards (both U5 and U3)?

3. Can someone explain the error near the capacitator network/array?

In your Prototyp Platine document, you say in German: Es müssen an den Arduino Pins 12,13,14,15 die Verbindung zu den Kondensatornetzwerk entfernt werden. Sollte das Kondensatornetzwerk noch nicht eingebaut sein die entsprechenden Beine
einfach bei Seite biegen oder abschneiden. and Google Translate says: It must be removed to connect to the Arduino Pins 12,13,14,15 to the capacitor network. If the capacitor network is not yet installed the corresponding legs just bend or cut off at page.

Can someone please explain this? What needs to be removed, and which pins need to be bent and why?

Also, on page 30 of Prototyp Platine (about odometry error), there is a photo in which four PCB traces are scratched/damaged.
However on my PCB (v1.2), there are five lot pads on those same traces, and they are not connected? What do I need to do with this?

4. Where should I solder the IRLIZ 44N MOSFET? I can't find a place for it on the main PCB?

5. Can you confirm the location of pin P35 on PCB (pinMotorMowRpm)? Is it next to the P20 (Button pin)?

I'm asking because on my PCB it says: "P35 Res Pin 49"!

6. Is it mandatory (do I must do it) to do the Workaround procedure described in WorkaRound20150530 document?

Thank you all in advance!

I would really appreciate your help to get this assembled and started!


Milos

 

[jack0]

welcome Milos

I'll try to clarify some points.

First the L298N accepts 25 W / 2 A per bridge, so for the mower motor, even with the 2 bridges in parallel it 'll be very short ... More on point 4.

1. That's also what I understood. The charging voltage regulation can be done with optional LM350T.

2. With reference to PCB version 1.2, you need the U3 to control the charging current. U5 measures current supplied to voltage regulators DC/DC for 3.3 V, 5 V and 10 V.

3. Analog inputs A12 to A15 receive the encoders impulses for odometry, which are very rapid (around 500 per secondes). If you put a low pass filter, you won't see them. It also applies for A11 if the mow motor has encoder. So the pins of the capacitors network corresponding to these inputs must not be connected. If your capacitor network is not yet soldered, you can just cut (or bend) the pins. If it is already installed, you have to cut the path leading to them by scratching the cupper on the pcb.
I guess the photo is an old one for pcb Version 0.5. On the version 1.2, as you have seen, there are lotpads which are already open, so you do not need to scratch your pcb.

4.There is no MOSFEt to solder on the pcb. They were used in old version but have been replaced since by H bridge MC33926. May I recommend you to check the wiki to get the updated version of the document you are using ? If you want to replace the MC33926 by MOSFET, which I did for the mower motor, just have a look there (instructions for the Ardumower board post=7578).

5. P35 is next to P20, right, but it is a reserve to access pin 49 of the Mega, which is not used. The MotorMowRpm is connected to P4, aside from P8 and P9 (odometry).

6. Your encoders signals will look better if you do it. These resistors are pull-up for the odometry and mow motor inputs.

Hope it helps

 

[etmilosk]

Thank you Jacques, your reply helps a lot.

I understand most of it, however I would like to ask you to clarify a bit more some of them, and, if I may, ask a couple of new questions:

2. So, are you saying that I only need the U3 and the U5 is optional?

3. Great, I understand everything.

4. With regards to you #4 answer and the comment about the L298N:

[ul]
[li]4.1 If I use MOSFET to drive the mower motor like you did, will I still have the possibility to modulate the mower motor rpm (for saving power and decreasing noise, etc)?[/li]
[li]4.2 Regarding the limitation of L298N, what do you think, would it be possible to drive the mower motor with two L298Ns connected in parallel? And to have the pcb driving both L298Ns at the same time (I mean driving them regarding the mowRPM via PWM, not power, I would power the L298Ns directly from the batteries)?[/li]
[li]4.3 The mower motor which I plan to use draws 0.5A with no load (@24V) and 1.9A when loaded at about 50%. What do you think, would a single L298N with an added fan be enough to drive it?[/li]
[/ul]

============================================ // new questions

7. I was planning to use the KY-040 rotary encoder for odometry ( link ) but I would connect them to the wheel shafts, which means that they would turn very slowly, around 20 rpm. And this encoder has 20 ticks per revolution. What do you think, will it be too slow or too incorrect for the code? Can I compensate for this in the code (I believe it's possible)?

8. Can someone tell me what is the exact number (model, part nubmer) of the 1.5KE diode you are using on the main Ardumower PCB board? It is the D2 diode. There are dozens of 1.5KE diodes with different voltage and current ratings, and each shop tell me that I must have a specific number/model.



Btw, I am using the latest documentation downloaded from the github, but I am also looking at the wiki since I can't understand all the documentation, and yes, I saw the MOSFET only on wiki, not in the pdf files.


Thanks for your help once again, regards!

 

[jack0]

Hello Milos

2. The system is open and very flexible, so you can choose which part and function you want to get or change or leave. I just answer your question about what are INA modules needed for. You can also replace these modules by other ones if you want, ACS712 for instance.

4.
1- yes, because a H bridge is made with MOSFET (see wikipedia H bridge). But you cannot reverse the rotation.
2- the 2 bridges of a L298N connected in // allow 4 A or 50 W. if you connect 2 L298N in //, that 4 bridges altogether, so 8 A or 100 W. But then it may be easier to use another more powerful bridge. Just have a look in the shop, I think you can find what you need. It is not a problem for the pcb to drive the H bridges, it just send a signal, not power. For the main supply of the motor, a protective board is really recommended. Read the "Workshop protector board.pdf" from Jurgen Lange (in german and in english), it's very demonstrative.
3- I'm not an electrician, but in your 1st post you wrote your motor is a 24 V 80 W. When the grass is thick, or high, or wet, the regulation will try to keep the rpm, hence more current will be pulled by the motor. I will not assume the motor will always be at less then 50% of its maximal power. And you also have to consider the starting current (well explained in the wiki).

7. That 's very low. The recommended motor gives 13.5 tics/cm, with yours it will be 1 tic each 4 cm (straight line, wheel of 25 cm diameter). In other words 6.7 tics/s compared to ~ 500. But if you don't use odometry, just to know is the robot is stucked, it should be enough.

8- It is a 30 A one, it was intented to avoid the mower teller to run in the wrong direction, but it is optional and it is not provided in the accessories set.

Greets