Voltage drops when turning on circuit with Arduino, boost converter, H-bridge

Hello All,
I'm building this circuit here:

To ring an antique phone that I've got. Just the phone ringer part, not the bluetooth and all that.

I've got it powered off a USB charger which can source 750mA. The circuit works great once it's powered up and draws a few milliamps in standby and maybe 100mA when actually ringing the phone, but when I initially switch it on it on it draws the full 750mA that the charger is capable of sourcing, and voltage is only 2.6V. It does this for as long as 15 seconds, sometimes even longer.

I'm assuming it's the boost converter getting up to the full 55V, but in the meantime the solenoid is basically a dead short so it can't get up to the full 55V. Is there a way to mitigate this inrush current?

I tried putting pull-down resistors on the input side of the H-bridge so that even before the Arduino has a chance to boot up (which it can't do while the voltage is dropped so low), the H-bridge outputs are disabled. Am I barking up the right tree?

Circuit attached for your perusal. Thank you for your help, I'm really close to finishing this one up :slight_smile:

I'm assuming it's the boost converter getting up to the full 55V

Probably not, since 220uF charged to 55 V is 0.33 Joules, and 5V*.75A*15s = 56 Joules.

You need to figure out why the circuit is drawing so much current. Since the circuit posted is not complete, or even correct (C2 and C18 are drawn as resistors) we can't do that for you.

Sorry for the confusion, I changed the Sparkfun circuit over to 0805 package and it looks like I got a little happy with the Change Package command. Attached is a revised schematic, a picture, and my board layout.

There’s not much else to the circuit than what’s shown in the schematic, I have the arduino connected to INA1/INA2, and power is provided directly by the USB wallwart. There’s a 100uF/.1uF filter cap combo on the arduino. Here’s what I’ve tried by way of troubleshooting:

  • Disconnected the boost and h-bridge part from the arduino and powered it separately. The large inrush current appears local to this circuit.

  • Disconnected the solenoid. The problem remained, so that eliminates my theory about the solenoid being a dead short.

The other problem in troubleshooting this is that the warm-up time is variable. Right now it’s only doing it for a few seconds and I’m not seeing the longer startup times that I was earlier. But sometimes it just gets stuck at 2.6 or 2.7V and doesn’t seem to be able to break out of it. Which would seem to indicate some kind of short, but I resoldered all the power/ground interconnect wires with no effect.

Phone Ringer Schematic Rev1.pdf (38 KB)

0506171216.jpg

Phone Ringer Rev1 board.pdf (48.8 KB)

even before the Arduino has a chance to boot up (which it can't do while the voltage is dropped so low),

I don't see an Arduino in your schematic.

ohnoezitasploded:
I have the arduino connected to INA1/INA2, and power is provided directly by the USB wallwart. There's a 100uF/.1uF filter cap combo on the arduino. Here's what I've tried by way of troubleshooting:

  • Disconnected the boost and h-bridge part from the arduino and powered it separately. The large inrush current appears local to this circuit.

  • Disconnected the solenoid. The problem remained, so that eliminates my theory about the solenoid being a dead short.

So to review, on the 5V rail provided by the USB charger I have:

  1. Atmega328, without a regulator but with filter caps (FTDI chip is separately powered by my laptop and only connected via ground, when it's connected at all)
  2. Wireless receiver module
  3. Boost circuit and H-Bridge

However, when I disconnect (1) and (2), the problem remains, which is why I think the circuit shown in the schematic is the issue.