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More motor survey

A project log for Wearable Haptic Sensor

A wearable haptic sensor for gaming

Peter WalshPeter Walsh 06/16/2022 at 14:230 Comments

I got 30 more motors, and did another motor survey of current requirements. The results are below, the chart shows the current draw of 30 motors run at 3.0 Volts:

Key takeaways:

1) The new batch draws roughly 50 mA (each), which is more in line with datasheet specs, as opposed to the previous batch of motors which drew 30 mA. The new batch is also smaller (8mm dia, instead to 10mm), and has short leads.

2) Coin cell motors with short leads are more difficult to manage. Quite possibly these will not easily mate to a flex-PCB due to the short leads.

3) The current measuring jig works pretty well.

The right answer is probably to order high-quality motors from reputable sources, rather than eBay bargain basement units. The price for eBay units is about $0.30 each, while the DigiKey price is around $2.50 each (qty: 10).

For the near term (ie - development), it makes better sense to order a pile of cheap motors from eBay, then check the current draw and toss the one or two that are wildly out of spec.

A hypothetical product with 6 (one strip) or 12 (two strips) motors would require $15 or $30 for the motors alone.

Another right answer is probably to use a fixed-current driver for the motors. The TLC5917 is an LED driver, but the PWM outputs should work well for the motors. Current limit up to 130 mA set from a single resistor, and PWM managed by the chip itself. Price: $1.50 each (qty: 10).

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