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High speed relay options comparing to reed relays

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fastline

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We are trying to switch both AC and DC with the same device. AC is approx .1-5VAC with 1-200hz, 5A, and DC is 15V, 5A. standard relays cannot switch fast enough for us and I found that the reed relay works great. However, to get these specs, these suckers are EXPENSIVE! Is there a solid state device that can switch a variable AC form AND DC? If not, is there something that can do the AC since that seems to be the issue?
 
Why does it need to be one device? A solid-state DC (not AC) relay should be able to switch both the AC and DC signals but, since 5A double-pole solid-state relays are not common, you may need to use two relays.
 
It really does not need to be one device but lag time between them should be the same so using the same device should help with this. They are basically turning two systems off that need turned off at the time time. Reeds will perform differently than SSR.

I thought a DC SSR would NOT switch AC and would drop out at zero crossing? Load required to operate?
 
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I thought a DC SSR would NOT switch AC and would drop out at zero crossing? Load required to operate?
A DC SSR will switch AC or DC. It's the AC SSR that drops out at zero crossing and requires a minimum load to operate.
 
A DC SSR is essentially two mosfets wired in series, either common source or common drain. As long as the DC rating is greater than the AC peak voltage they will work fine for AC.

And in your case, a DC SSR will work better for the AC portion than an AC SSR would. This is because an AC SSR is either a triac or a pair of SCRs. They have a saturated ON voltage of more than a volt that would eat up a fair part of your 5VAC, and not let anything through for voltages loser than their saturation voltage.

A mosfet switch will just be a resistance that, if chosen properly, can have far less insertion loss than an AC SSR would. But you want to choose it based more on it's ON state resistance, than on it's current rating.
 
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