My variable speed drill switches turn into ON/OFF switches :-(

  • Thread starter Thread starter Bruce Ratcliffe
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SUMMARY

The discussion centers on the challenges faced by Bruce Ratcliffe in using Bosch 25Amp, 24 VDC drill switches for controlling wheelchair motors in eCars. The switches often fail due to voltage spikes generated by the inductive motors. Participants recommend using a full wave bridge rectifier (FWBR) and protective diodes to mitigate these spikes, with specific diode types suggested for optimal performance. Bruce is advised to use a 0.1uF ceramic capacitor to further smooth out voltage fluctuations and is exploring the use of MOSFETs to enhance circuit reliability.

PREREQUISITES
  • Understanding of inductive loads and voltage spikes
  • Familiarity with diodes, specifically fast recovery diodes
  • Knowledge of full wave bridge rectifiers (FWBR)
  • Basic electronics skills, including soldering and circuit design
NEXT STEPS
  • Research the specifications and applications of fast recovery diodes
  • Learn about full wave bridge rectifier configurations and their benefits
  • Study the characteristics of MOSFETs, particularly the IRL2505 model
  • Explore methods for measuring voltage spikes using oscilloscopes
USEFUL FOR

Electronics hobbyists, educators in robotics, and engineers working with motor control circuits who are looking to enhance the durability and reliability of their designs.

  • #31
Your description of 'doesn't work' seems to describe the 80% chance of an 'operator errer.'

Open up the first one you did, the one that works.
Put it side by side to the one that does not work.
Trace and compare every wire, terminal label and part number on each.
80% chance that they are either not identical or not connnected.
Pay attention to polarities.

The other 20%? -- bad component.

(Sorry, no authoritative reference, just many decades of "Arrgh sh*t, what now!")

Cheers,
Tom
 
Last edited:

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