DC-DC SSR's and inductive loads

Projects General Guidance
1

I have a 24V DC electric actuator that i want to use to operate the throttle on a 1951 Stork ricardo AR216 slow running diesel engine. Data sheet for this actuator : https://cdn.linak.com/-/media/files/data-sheet-source/en/linear-actuator-la33-data-sheet-eng.ashx

My actuator has integrated end stops but no position feedback. To know what the actuator is up to i want to install a linear potmeter like this : https://www.microlectra.nl/files/5ed2d92955d7e1eb94f30c81efe75526/lpcpdf

For input I want to use a 180° absolute rotary encoder like this ; http://dis-sensors.com/download/pdf/QR40-180HB-VK.pdf

By this encoder i can input a desired throttle position, with the linear potmeter i have position feedback from the actuator, finally i ordered 4 DC-DC SSR like this ; https://www.jameco.com/Jameco/Products/ProdDS/2218126.pdf

Plan is to write a sketch that controls the actuator, 2 ssr's to push out, 2 for inverted polarity to retract. I could write the sketch so that the ssr's are PWM controlled to go fast if the difference between input and output is big and slow down proportional to the distance to fo.

What worries me (besides things that i may have overlooked) is that with inductive loads one should wire a diode into the circuit (see data sheet), but how to do that with reversable polarity ?
I assume that PWM is going to amplify the effect that the diode is supposed to prevent ?

Any suggestions much appreciated

2

Look for an H-bridge motor driver. They are "reversible".

Plan is to write a sketch that controls the actuator, 2 ssr's to push out, 2 for inverted polarity to retract.

Unless you have a negative power supply available, it takes 4-contacts to switch polarity. (It can be done with a DPDT relay.)

What worries me (besides things that i may have overlooked) is that with inductive loads one should wire a diode into the circuit (see data sheet), but how to do that with reversable polarity ]

You might also have trouble with reverse voltage across a DC SSR. And, most AC SSRs wont work because they have a TRIAC and they can't turn-off with DC (after being turned-on).

I really haven't though about this so I could be wrong, but I assume an H-bridge works without a diode because when one pair of transistors/MOSFETs turns off, the other pair turns-on, providing a current-path for the reverse EMF.

3

The actuator includes a motor that turns a spindle. To reverse the direction, you reverse the motor voltage, best with an H-bridge, which also allows for PWM control.

An H-bridge includes low-side and high-side drivers, which can not be constructed with the low-side DC SSR.

4

Thanks !!! Found this Cytron 10Amp motor shield that fits my needs perfectly for 20$ !

5

Hi,

sluiswacht:
Thanks !!! Found this Cytron 10Amp motor shield that fits my needs perfectly for 20$ !

Don;t keep it to yourself, post a link...

Tom...