Stepping down Traco TEC-30923 to +-12V

mybud

mybud

Well-known member
I'm looking to step this down from +-15VDC to +-12VDC to harmonise with normal modular synth voltages.

My question is what resistor values (voltage divider arrangement) would work here. I acknowledge that running things at 15V might be ok but don't want to risk messing things up by making unsupported assumptions.

Any help gratefully accepted. TIA.
 
Using the TEC 3-0922 would do it
Edit, as @jwin615 pointed out, the 3-1222 if you want to use a 9-18v power supply.

Is there is a voltage regulator before the traco ? What circuit is it ?
 
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You'll need a 1/4 ratio in the divider
Like 30k/120k
If it's just for a bread board or experimenting, fine
But I wouldn't deploy this in a finished project
You're loosing 20% potential output current using the 15v model already. 125mA vs 100mA output. Loosing a tad bit more in the divider. 100-200uA. Not a ton.
 
What is the current draw per rail for this circuit? If your circuit draws any significant amount of current, output voltage at the voltage divider is going to sag and fluctuate unless you use very low value resistors. For a stiff rail you'd choose your voltage divider current to be at least 10 times your load current, so for example if your load current is 10 mA, divider current should be 100 mA at least. Ohm's law says R=V/I, so 12V/0.1A=120 Ohms (!) total resistance for the voltage divider. In other words, with a load current of 10 mA, your voltage divider should be 24R/96R (12/15=0,8, so resistor to ground should be 0,8 * total resistance) to get a somewhat stiff 12V-ish. That's going to create a looot of heat. Also, your rail now draws over 100 mA.
In other words, whether a voltage divider is going to work and which values it needs depends on the load current of your circuit.
 
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lowpitch said:
What is the current draw per rail for this circuit? If your circuit draws any significant amount of current, output voltage at the voltage divider is going to sag and fluctuate unless you use very low value resistors. For a stiff rail you'd choose your voltage divider current to be at least 10 times your load current, so for example if your load current is 10 mA, divider current should be 100 mA at least. Ohm's law says R=V/I, so 12V/0.1A=120 Ohms (!) total resistance for the voltage divider. In other words, with a load current of 10 mA, your voltage divider should be 24R/96R (12/15=0,8, so resistor to ground should be 0,8 * total resistance) to get a somewhat stiff 12V-ish. That's going to create a looot of heat. Also, your rail now draws over 100 mA.
In other words, whether a voltage divider is going to work and which values it needs depends on the load current of your circuit.
Click to expand...

Yes thanks, @lowpitch. There’s a lot more to this than meets the eye, I gather.
 
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