Test Measurement - Multi-Meters, Small Test Tools.

Wednesday, February 28, 2018

DC Small Motor Control using PWM

message: Greetings, I have a kit motor controller. I works just fine. It uses the NE556. I read some where ( on a NE555 )that I can change one of the capacitors with a variable capacitor to get the full range of frequencies out of the NE555.

 Is it possible to get adjustable frequencies out of the NE556? I have the circuit drawing. Is there any one I can send the diagram to so they could tell me which capacitor I can change? Thank you,

BR USA


PWM DC Motor Speed Control - This is a circuit for controlling the speed of small DC motors, it works nicely as a speed controller for an HO or N gauge model railroad.

DC Motor Control for Low Power

Timing 555 Motor Speed - It uses a variable frequency 555 astable. The astable triggers a monostable that produces pulses of a fixed width. At lower frequencies, the monostable pulses are infrequent and the output is high about 20% of the time.

delabs

Isolation Resistance and Insulation Resistance

message: what is insulation and isolation resistance, why and how it is measured? what are the consequences if it is not measured? 2008


Isolation Resistance and Insulation Resistance are both related to each other. Isolation Resistance could be in Giga Ohms and Tera Ohms and includes Surface Resistivity.

Insulation Resistance will be in the Range of Mega Ohms and Giga Ohms. You could say Isolation Resistance is a Tera Ohm and Giga Ohm Measurement Test.

Isolation Resistance and Insulation Resistance

Les us assume a 5KV Isolation Opto-Coupler on a Glass Epoxy PCB. You could Measure its Isolation or Insulation Resistance and it will be in the range of 1 Tera Ohms in a good PCB.

A good PCB will have a Slot Routed below the Opto Coupler for High Isolation. This will ensure Dust and Grime along with Moisture will not form a Leakage path below opto-coupler.

Use a Megohmmeter for Insulation Resistance of Transformers, Coils and Relays. Use a Teraohm Meter to measure Isolation Resistance in Opto Couplers, PCB, Ceramics and Capacitors.

Megohmmeter is a special type of ohmmeter used to measure the electrical resistance of insulators. Insulating components, for example cable jackets, must be tested for their insulation strength at the time of commissioning and as part of maintenance of high voltage electrical equipment and installations.

6520 Programmable Teraohmmeter makes resistance measurements up to 10 PΩ. Whether used in automated mode via the Guildline developed TeraCal Software or as a stand-alone meter,

Practical Electronics

Practical Electronics
Basic Electronics, EE Reference Resource, Analog, Digital, Power and Electrical.

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