Part requirements for a DC solenoid project

[JJ2430]

I received my new uC and tested connections on breadboard with suggestions provided by Mike. So far everything work as it should and the circuit is very stable, even on uC boot-up: GPIO 5 is indeed providing high impedance so resistor is no longer needed between GPIO and INA. The solenoid's response is fast and without glitch. For now the circuit is currently running on a 12VDC psu and the uC uses Li-Ion 5V. I will perform further tests and assemble the final PCB with solder. I also received the Lipo 6A. Tested it to verify voltage of each individual cell and total. The battery looks in proper shape at 3.81V each cell for a total of 15.24V. This is the usual "resting" charge and corresponds to about 35% of charge. The intelligent charger is on the way. Will give the battery 2 to 3 cycles to "break it", as recommended, before putting it under more serious use. I'm also waiting for the balance protection pcb and buck converter. I ordered a Lipo low voltage monitor/buzzer that I will install in the circuit and adjust to 3.7V per cell in order to avoid undercharge.

I linked a video and attached pictures of the latest developments.

Previous connections before Mike's latest recommendations:

Latest connections:

Video:


I will implement the Lipo once the protection pcb and buck converter are here. I will follow Rj's recommendation of unplugging and removing battery from rig for charging since the charger monitors balance as well. I've been reading a lot on Lipo technology over the last days and the precautions to take to enhance battery life for one, and also to prevent hazards such like explosions and fire. It is preferable to charge the battery in a safe environment and not tethered to the system it is powering.

I will connect the Lipo the same way as depicted in the image below. The pcb will be permanently connected to the system and the battery removed for each charging cycle.

 

[Pommie]

Just out of curiosity, why have you chosen a Wemos. Do you intend to connect to it via wifi and control it that way?

Mike.

 

[JJ2430]

Yes, in fact the Wemos connects to a computer via Bluetooth as a BT device--like a BT keyboard--and interacts with a program, a game engine in fact such like Unreal Engine to create immersive and interactive virtual environments. Every time the S2 press switch is activated the Wemos is programmed to send a specific character which the program recognizes and performs an action based upon that. The 2 solenoids application is experimental for the moment but it will be implemented into a game controller that provides haptic feedback, such like in a flight or race simulator motion platform. Watch vids of my most recent projects for racing simulation

My daughter trying my simulator for the first time:

Early development of the motion platform:

By pressing the switch the solenoids would trigger an action on my simulator platform, such like a control giving a kick when a button is pressed--like a turbo pressure switch for instance--the program registers that and tells the car, plane, etc to go faster in-game.

Edit: and the reason why the rechargeable battery to power the rig is because I intend to use that technology on portable game controller devices for vr applications that could be used in an environment that is free of wires,

 

[Pommie]

Ahhh, you're using the esp32 version, I'd assumed esp8266. Have you considered putting a second MOSFET in circuit connected to the second driver for possible future expansion?

Mike.

 

[JJ2430]

That's right, the EPS32 with BT antenna, It is a very powerful device and the range is impressive for what I need: 30 feet of signal freedom, through walls, etc. In the moment one single MOSFET is providing current to the 2 solenoids. It works very well and since the solenoids cycles are not very long, about 250 milisecs for each switch activation, it doesn't get very hot but I plan to install a good heat sink when the system undergoes more lenghty service.

Edit: using the INB/OUTB of the gate driver connected to a second MOSFET could be an interesting idea to provide a second level of control since it could send different instructions from the Wemos and thus, as you say, provides room for future expansion.

 

[JJ2430]

Hi,
The DC-DC step down buck converter that I use to convert voltage from 16v 4s Li-Ion battery down to 9v for Wemos input Vin is introducing electronic noise onto the circuit and in the Wemos regulator. I can hear a constant buzz when I get my ear close to the board. This buzz is not present when Wemos is connected directly to a 12v psu. I've read that buck converters are notorious for introducing audible acoustic noise. Do you know of a way to mitigate/reduce the noise generated by a buck converter? A diode in serie, etc? It is not audible when circuit is at a distance from ears. But beside the unwanted acoustic problem can this be harmful for the uC in the long term? Tks

 

[JJ2430]

A suggestion to alleviate the ripple noise is to add an ESR ceramic capacitor at the output of the buck converter. But there seem to be some minor negative consequences of doing so. What do you think?

 

[Nigel Goodwin]

Hi,
The DC-DC step down buck converter that I use to convert voltage from 16v 4s Li-Ion battery down to 9v for Wemos input Vin is introducing electronic noise onto the circuit and in the Wemos regulator. I can hear a constant buzz when I get my ear close to the board. This buzz is not present when Wemos is connected directly to a 12v psu. I've read that buck converters are notorious for introducing audible acoustic noise. Do you know of a way to mitigate/reduce the noise generated by a buck converter? A diode in serie, etc? It is not audible when circuit is at a distance from ears. But beside the unwanted acoustic problem can this be harmful for the uC in the long term? Tks

Not an issue electrically - don't put your ear next to the board

 

[KeepItSimpleStupid]

Hagstrom Electronics has a USB interface that will interface to the 'mouse'. Rotary solenoids are probably faster. They dont like 100% duty cycle. Dont forget the activation delay.