• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 30 subscribers
  • Views 1516 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

DRV101: Solenoid driver advice needed

DRV101: Solenoid driver advice needed

Simon Moxon
Prodigy 80 points

Part Number: DRV101

First of all, I would like to thank you again for the help and advice given in my previous question relating to the DRV10x solenoid drivers.  I settled on the DRV102 and created a PCB with 5 DRV102's, 10 diodes, 5 0.47uF capacitors, and 5 10kOhm pots to adjust the duty cycle.  These have worked great and I can now play the full range of my sax using just one hand.

I put some video here to show the design in action.

My thoughts have now gone back to one of the earlier responses to my original question, where it was suggested I could use the ULN2003A or the TPL7407LA.

My holding voltage at the moment is about 1.9v, which I understand may be too low for these IC's.  However, at this stage, I am more interested in the function of these IC's and the Octal power switch detailed in the DRV102 spec.

The scenario I envisage would be a solenoid is activated and held in position.  A second solenoid is then activated and held in position or activated, released, and activated again before being held in position.  The two solenoids are then released, then activated together.

Are any of the array controllers suitable for such a task?  I cannot get my brain to comprehend how they could do this.

My aim is to reduce the overall size of my PCB and the number of components.  I did look at using the DRV103's (I purchased 10 of them), and may revisit them, but I had great difficulty working with them, namely when trying to solder them into my circuit.

If I can reduce the size of the circuitry, I may be able to apply the same concept to smaller instruments.

Thanks in advance for any advice.

Simon

  • 0
    TI__Genius 15780 points

    Hi Simon,

    Thanks for sharing the video of your system, that's a pretty cool application! 

    You mention that the holding voltage for the solenoids is 1.9V. Does this mean that the output voltage is 1.9V? The TPL7407LA shouldn't have any issue with driving loads with this voltage. Do you need the fully current carrying capability and PWM functionality of the DRV devices?

    Also, for your description below, are you looking for logic to make the below happen?

    "The scenario I envisage would be a solenoid is activated and held in position.  A second solenoid is then activated and held in position or activated, released, and activated again before being held in position.  The two solenoids are then released, then activated together."

    What is the timing between these events?

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    Prodigy 80 points

    Hi Alek,

    I'm putting 11.1v through the circuit from a LiPo battery (2200mAh).

    The solenoids are rated at 6v, but have coped ok with the extra voltage that initially goes through them.  They need this higher voltage to push the keys down as some of them are quite heavily sprung. 

    I've tried to offset this by placing a small spring on the push side of the solenoid, and preventing the solenoid fully returning to its rest position (the spec for the solenoid suggests it is quite weak at the first part of its stroke).

    So, my initial input is 11.1v, which holds for .5 seconds using the 0.47uF capacitor, then the DRV102 drops to the lower voltage of about 1.9v.

    I'd like one of these arrays to be able to do the same thing, but be capable of controlling multiple solenoids independently.  At the moment, I'm using 5 DRV102's to control 5 solenoids.

    Each driver is controlled by a switch on the sax.

    In the scenario I gave, which is just a random example, this would be me playing the instrument and pressing the switches to activate each solenoid; it is not automated.

    Basically, I need each solenoid to be driven independently of each other and was unsure if something like the TPL7407LA would be able to do the same job that my 5 DRV102's are doing at the moment.

    My goal is to reduce the size of the circuit so I can add more solenoids if needed and apply the concept to a smaller instrument, such as flute or clarinet.

    Please note, I have a very limited understanding of electronics.

  • 0 in reply to Simon Moxon
    TI__Genius 15780 points
    Hi Simon,


    If the switches on the sax are providing the logic signals, and the activation current for the solenoids is below 500mA each, then the TPL7407LA should be able to work here. Each channel of the device is independent of the others, and all are controlled by their own input/enable pin.


    Do you foresee any problems using a device like this?


    Thanks,


    Alek Kaknevicius
  • 0 in reply to Aleksandras_Kaknevicius
    Prodigy 80 points

    Great, it sounds like it will do the job in terms of logic!

    I really couldn't get my head around how it could do the duty cycle at different times for multiple solenoids.

    My only concern will be the amperage for activating the solenoid.  They are rated at 300mA, but my experience using them is that they draw a lot more on this to push down the keys on the instrument.... I've seen up to 2 amps on my meter during testing.

  • 0 in reply to Simon Moxon
    TI__Genius 15780 points

    Hi Simon,

    I just want to clarify some things before confirming the solution :). The TPL7407LA does not automatically duty cycle the outputs. In this case, you would need a PWM signal going into each of the inputs of the device to duty cycle the outputs. You can duty cycle each of the outputs separately though, so each one is capable of having a different duty cycle. It's a simple device, so whatever is put on the input will be reflected on the output.

    300mA would be no problem for a single channel of the device to handle, but 2A would require paralleling a few channels together to increase current capability.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    Prodigy 80 points

    Hi Alek,

    please excuse my lack of knowledge.

    So, the TPL7407LA is more like a relay for switching a high load device on and off with a much lower current.

    I will certainly need each switch to have an initial high voltage that drops to a much lower voltage.  In my current setup, 11.1v initial voltage to activate the solenoid, that then drops to around about 2v after half a second.  It then needs to maintain this voltage to hold the solenoid until I want to release the key.

    In your description, does this mean I will require 2 different power sources, 1 for each voltage?

    As for the amps, I'll have to try and measure this again.  I'm sure that they do not all need such a high current draw, and it's possible I may have used a damaged solenoid when I initially took that measurement.  I'm getting well over 1 hour out of a 2200mAh battery, so I figure the draw must be lower than 2 amps.