Electronics/Tenma 72-8350 PSU

Tenma 72-8350 PSU

Lightweight SMPS lab power supply
Equipment Information
Status	Unknown
Manufacturer	Tenma (OEM: Mastech)
Model	72-8350
Hackspace Information
Induction Required	Yes
Induction Information	Here
Card RFID Enabled	No
Owner	Tom (On Loan)

The Basics

A very useful unit which can output anywhere from 1-20 volts DC at 0-5 amps. Useful for higher current loads. The output voltage is minimum ~0.7 volt when unloaded.

This power supply has a CC/CV mode BUT unlike the Tagasaki power supply due to a design flaw shorting the output may cause failure of the power supply's switching transistors. Whilst not terribly difficult to replace it is best avoided. Therefore, please avoid shorting or significantly overloading this power supply.

This is a very lightweight power supply because it uses a switchmode design. This also means it is efficient. A small fan has been added by Tom to keep the power supply cool.

The digital displays tend to drift a little at a set point but the output voltage is usually steady. The displays have been modified for a faster update rate as described by Mikes Electric Stuff here: https://www.youtube.com/watch?v=6LEN_HNFK40

Safety

You must read the safety documentation in this link before using this equipment.

The maximum output of the power supply of around 21 volts is below the SELV limit. This means it is *generally* safe to touch. However, it is still possible to pass a dangerous amount of current through your body using this unit, for example through open sores. The current is also sufficient to cause burns if you are careless.

The output current is more than sufficient to release smoke from devices and wires, which could be a fire hazard. You should ensure you always set an appropriate current limit.

Uses

The CC mode can also be used to power high-power LEDs without use of a resistor. Simply set the current limit to the rating of the LED. To read and set the current limit, set the voltage to zero, short the output of the power supply, increase the voltage dial until the "CC" LED illuminates then adjust current until the desired limit is reached. DO NOT SHORT THE OUTPUT WHILE THE VOLTAGE IS ABOVE 3 VOLTS OR THE POWER SUPPLY MAY BUZZ/OSCILLATE AND FAIL.

Another use for the CC mode is to "bring up" a project slowly to avoid smoke release. Set the voltage to the desired limit, but before connecting your load, set the current to zero. Connect your load, then slowly increase the current. If all is well, the voltage will rise with the current increase and the load will work. If there's a problem, voltage will stay low but current will continue increasing. If you see this, you can disconnect the load before damage occurs.

Induction

Ask on the mailing list for volunteers to demonstrate the use of any of the test equipment.